File indexing completed on 2025-03-09 03:55:08

 /*
  * transupp.c
  *
  * SPDX-FileCopyrightText: 1997-2011, Thomas G. Lane, Guido Vollbeding.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains image transformation routines and other utility code
  * used by the jpegtran sample application.  These are NOT part of the core
  * JPEG library.  But we keep these routines separate from jpegtran.c to
  * ease the task of maintaining jpegtran-like programs that have other user
  * interfaces.
  */
 
 /* Although this file really shouldn't have access to the library internals,
  * it's helpful to let it call jround_up() and jcopy_block_row().
  */
 #define JPEG_INTERNALS
 
 #include "jinclude.h"
 #include "jpeglib.h"
 #include "transupp.h"       /* My own external interface */
 #include <ctype.h>      /* to declare isdigit() */
 
 
 #if TRANSFORMS_SUPPORTED
 
 /*
  * Lossless image transformation routines.  These routines work on DCT
  * coefficient arrays and thus do not require any lossy decompression
  * or recompression of the image.
  * Thanks to Guido Vollbeding for the initial design and code of this feature,
  * and to Ben Jackson for introducing the cropping feature.
  *
  * Horizontal flipping is done in-place, using a single top-to-bottom
  * pass through the virtual source array.  It will thus be much the
  * fastest option for images larger than main memory.
  *
  * The other routines require a set of destination virtual arrays, so they
  * need twice as much memory as jpegtran normally does.  The destination
  * arrays are always written in normal scan order (top to bottom) because
  * the virtual array manager expects this.  The source arrays will be scanned
  * in the corresponding order, which means multiple passes through the source
  * arrays for most of the transforms.  That could result in much thrashing
  * if the image is larger than main memory.
  *
  * If cropping or trimming is involved, the destination arrays may be smaller
  * than the source arrays.  Note it is not possible to do horizontal flip
  * in-place when a nonzero Y crop offset is specified, since we'd have to move
  * data from one block row to another but the virtual array manager doesn't
  * guarantee we can touch more than one row at a time.  So in that case,
  * we have to use a separate destination array.
  *
  * Some notes about the operating environment of the individual transform
  * routines:
  * 1. Both the source and destination virtual arrays are allocated from the
  *    source JPEG object, and therefore should be manipulated by calling the
  *    source's memory manager.
  * 2. The destination's component count should be used.  It may be smaller
  *    than the source's when forcing to grayscale.
  * 3. Likewise the destination's sampling factors should be used.  When
  *    forcing to grayscale the destination's sampling factors will be all 1,
  *    and we may as well take that as the effective iMCU size.
  * 4. When "trim" is in effect, the destination's dimensions will be the
  *    trimmed values but the source's will be untrimmed.
  * 5. When "crop" is in effect, the destination's dimensions will be the
  *    cropped values but the source's will be uncropped.  Each transform
  *    routine is responsible for picking up source data starting at the
  *    correct X and Y offset for the crop region.  (The X and Y offsets
  *    passed to the transform routines are measured in iMCU blocks of the
  *    destination.)
  * 6. All the routines assume that the source and destination buffers are
  *    padded out to a full iMCU boundary.  This is true, although for the
  *    source buffer it is an undocumented property of jdcoefct.c.
  */
 
 
 LOCAL(void)
 do_crop (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
      JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
      jvirt_barray_ptr *src_coef_arrays,
      jvirt_barray_ptr *dst_coef_arrays)
 /* Crop.  This is only used when no rotate/flip is requested with the crop. */
 {
   JDIMENSION dst_blk_y, x_crop_blocks, y_crop_blocks;
   int ci, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   jpeg_component_info *compptr;
 
   /* We simply have to copy the right amount of data (the destination's
    * image size) starting at the given X and Y offsets in the source.
    */
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       src_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, src_coef_arrays[ci],
      dst_blk_y + y_crop_blocks,
      (JDIMENSION) compptr->v_samp_factor, FALSE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     jcopy_block_row(src_buffer[offset_y] + x_crop_blocks,
             dst_buffer[offset_y],
             compptr->width_in_blocks);
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_flip_h_no_crop (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
            JDIMENSION x_crop_offset,
            jvirt_barray_ptr *src_coef_arrays)
 /* Horizontal flip; done in-place, so no separate dest array is required.
  * NB: this only works when y_crop_offset is zero.
  */
 {
   JDIMENSION MCU_cols, comp_width, blk_x, blk_y, x_crop_blocks;
   int ci, k, offset_y;
   JBLOCKARRAY buffer;
   JCOEFPTR ptr1, ptr2;
   JCOEF temp1, temp2;
   jpeg_component_info *compptr;
 
   /* Horizontal mirroring of DCT blocks is accomplished by swapping
    * pairs of blocks in-place.  Within a DCT block, we perform horizontal
    * mirroring by changing the signs of odd-numbered columns.
    * Partial iMCUs at the right edge are left untouched.
    */
   MCU_cols = srcinfo->output_width /
     (dstinfo->max_h_samp_factor * dstinfo->min_DCT_h_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * compptr->h_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     for (blk_y = 0; blk_y < compptr->height_in_blocks;
      blk_y += compptr->v_samp_factor) {
       buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, src_coef_arrays[ci], blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     /* Do the mirroring */
     for (blk_x = 0; blk_x * 2 < comp_width; blk_x++) {
       ptr1 = buffer[offset_y][blk_x];
       ptr2 = buffer[offset_y][comp_width - blk_x - 1];
       /* this unrolled loop doesn't need to know which row it's on... */
       for (k = 0; k < DCTSIZE2; k += 2) {
         temp1 = *ptr1;  /* swap even column */
         temp2 = *ptr2;
         *ptr1++ = temp2;
         *ptr2++ = temp1;
         temp1 = *ptr1;  /* swap odd column with sign change */
         temp2 = *ptr2;
         *ptr1++ = -temp2;
         *ptr2++ = -temp1;
       }
     }
     if (x_crop_blocks > 0) {
       /* Now left-justify the portion of the data to be kept.
        * We can't use a single jcopy_block_row() call because that routine
        * depends on memcpy(), whose behavior is unspecified for overlapping
        * source and destination areas.  Sigh.
        */
       for (blk_x = 0; blk_x < compptr->width_in_blocks; blk_x++) {
         jcopy_block_row(buffer[offset_y] + blk_x + x_crop_blocks,
                 buffer[offset_y] + blk_x,
                 (JDIMENSION) 1);
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_flip_h (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
        JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
        jvirt_barray_ptr *src_coef_arrays,
        jvirt_barray_ptr *dst_coef_arrays)
 /* Horizontal flip in general cropping case */
 {
   JDIMENSION MCU_cols, comp_width, dst_blk_x, dst_blk_y;
   JDIMENSION x_crop_blocks, y_crop_blocks;
   int ci, k, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JBLOCKROW src_row_ptr, dst_row_ptr;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   /* Here we must output into a separate array because we can't touch
    * different rows of a single virtual array simultaneously.  Otherwise,
    * this is essentially the same as the routine above.
    */
   MCU_cols = srcinfo->output_width /
     (dstinfo->max_h_samp_factor * dstinfo->min_DCT_h_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * compptr->h_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       src_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, src_coef_arrays[ci],
      dst_blk_y + y_crop_blocks,
      (JDIMENSION) compptr->v_samp_factor, FALSE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     dst_row_ptr = dst_buffer[offset_y];
     src_row_ptr = src_buffer[offset_y];
     for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks; dst_blk_x++) {
       if (x_crop_blocks + dst_blk_x < comp_width) {
         /* Do the mirrorable blocks */
         dst_ptr = dst_row_ptr[dst_blk_x];
         src_ptr = src_row_ptr[comp_width - x_crop_blocks - dst_blk_x - 1];
         /* this unrolled loop doesn't need to know which row it's on... */
         for (k = 0; k < DCTSIZE2; k += 2) {
           *dst_ptr++ = *src_ptr++;   /* copy even column */
           *dst_ptr++ = - *src_ptr++; /* copy odd column with sign change */
         }
       } else {
         /* Copy last partial block(s) verbatim */
         jcopy_block_row(src_row_ptr + dst_blk_x + x_crop_blocks,
                 dst_row_ptr + dst_blk_x,
                 (JDIMENSION) 1);
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_flip_v (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
        JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
        jvirt_barray_ptr *src_coef_arrays,
        jvirt_barray_ptr *dst_coef_arrays)
 /* Vertical flip */
 {
   JDIMENSION MCU_rows, comp_height, dst_blk_x, dst_blk_y;
   JDIMENSION x_crop_blocks, y_crop_blocks;
   int ci, i, j, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JBLOCKROW src_row_ptr, dst_row_ptr;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   /* We output into a separate array because we can't touch different
    * rows of the source virtual array simultaneously.  Otherwise, this
    * is a pretty straightforward analog of horizontal flip.
    * Within a DCT block, vertical mirroring is done by changing the signs
    * of odd-numbered rows.
    * Partial iMCUs at the bottom edge are copied verbatim.
    */
   MCU_rows = srcinfo->output_height /
     (dstinfo->max_v_samp_factor * dstinfo->min_DCT_v_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_height = MCU_rows * compptr->v_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       if (y_crop_blocks + dst_blk_y < comp_height) {
     /* Row is within the mirrorable area. */
     src_buffer = (*srcinfo->mem->access_virt_barray)
       ((j_common_ptr) srcinfo, src_coef_arrays[ci],
        comp_height - y_crop_blocks - dst_blk_y -
        (JDIMENSION) compptr->v_samp_factor,
        (JDIMENSION) compptr->v_samp_factor, FALSE);
       } else {
     /* Bottom-edge blocks will be copied verbatim. */
     src_buffer = (*srcinfo->mem->access_virt_barray)
       ((j_common_ptr) srcinfo, src_coef_arrays[ci],
        dst_blk_y + y_crop_blocks,
        (JDIMENSION) compptr->v_samp_factor, FALSE);
       }
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     if (y_crop_blocks + dst_blk_y < comp_height) {
       /* Row is within the mirrorable area. */
       dst_row_ptr = dst_buffer[offset_y];
       src_row_ptr = src_buffer[compptr->v_samp_factor - offset_y - 1];
       src_row_ptr += x_crop_blocks;
       for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks;
            dst_blk_x++) {
         dst_ptr = dst_row_ptr[dst_blk_x];
         src_ptr = src_row_ptr[dst_blk_x];
         for (i = 0; i < DCTSIZE; i += 2) {
           /* copy even row */
           for (j = 0; j < DCTSIZE; j++)
         *dst_ptr++ = *src_ptr++;
           /* copy odd row with sign change */
           for (j = 0; j < DCTSIZE; j++)
         *dst_ptr++ = - *src_ptr++;
         }
       }
     } else {
       /* Just copy row verbatim. */
       jcopy_block_row(src_buffer[offset_y] + x_crop_blocks,
               dst_buffer[offset_y],
               compptr->width_in_blocks);
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_transpose (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
           JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
           jvirt_barray_ptr *src_coef_arrays,
           jvirt_barray_ptr *dst_coef_arrays)
 /* Transpose source into destination */
 {
   JDIMENSION dst_blk_x, dst_blk_y, x_crop_blocks, y_crop_blocks;
   int ci, i, j, offset_x, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   /* Transposing pixels within a block just requires transposing the
    * DCT coefficients.
    * Partial iMCUs at the edges require no special treatment; we simply
    * process all the available DCT blocks for every component.
    */
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks;
          dst_blk_x += compptr->h_samp_factor) {
       src_buffer = (*srcinfo->mem->access_virt_barray)
         ((j_common_ptr) srcinfo, src_coef_arrays[ci],
          dst_blk_x + x_crop_blocks,
          (JDIMENSION) compptr->h_samp_factor, FALSE);
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         src_ptr = src_buffer[offset_x][dst_blk_y + offset_y + y_crop_blocks];
         for (i = 0; i < DCTSIZE; i++)
           for (j = 0; j < DCTSIZE; j++)
         dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_rot_90 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
        JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
        jvirt_barray_ptr *src_coef_arrays,
        jvirt_barray_ptr *dst_coef_arrays)
 /* 90 degree rotation is equivalent to
  *   1. Transposing the image;
  *   2. Horizontal mirroring.
  * These two steps are merged into a single processing routine.
  */
 {
   JDIMENSION MCU_cols, comp_width, dst_blk_x, dst_blk_y;
   JDIMENSION x_crop_blocks, y_crop_blocks;
   int ci, i, j, offset_x, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   /* Because of the horizontal mirror step, we can't process partial iMCUs
    * at the (output) right edge properly.  They just get transposed and
    * not mirrored.
    */
   MCU_cols = srcinfo->output_height /
     (dstinfo->max_h_samp_factor * dstinfo->min_DCT_h_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * compptr->h_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks;
          dst_blk_x += compptr->h_samp_factor) {
       if (x_crop_blocks + dst_blk_x < comp_width) {
         /* Block is within the mirrorable area. */
         src_buffer = (*srcinfo->mem->access_virt_barray)
           ((j_common_ptr) srcinfo, src_coef_arrays[ci],
            comp_width - x_crop_blocks - dst_blk_x -
            (JDIMENSION) compptr->h_samp_factor,
            (JDIMENSION) compptr->h_samp_factor, FALSE);
       } else {
         /* Edge blocks are transposed but not mirrored. */
         src_buffer = (*srcinfo->mem->access_virt_barray)
           ((j_common_ptr) srcinfo, src_coef_arrays[ci],
            dst_blk_x + x_crop_blocks,
            (JDIMENSION) compptr->h_samp_factor, FALSE);
       }
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         if (x_crop_blocks + dst_blk_x < comp_width) {
           /* Block is within the mirrorable area. */
           src_ptr = src_buffer[compptr->h_samp_factor - offset_x - 1]
         [dst_blk_y + offset_y + y_crop_blocks];
           for (i = 0; i < DCTSIZE; i++) {
         for (j = 0; j < DCTSIZE; j++)
           dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
         i++;
         for (j = 0; j < DCTSIZE; j++)
           dst_ptr[j*DCTSIZE+i] = -src_ptr[i*DCTSIZE+j];
           }
         } else {
           /* Edge blocks are transposed but not mirrored. */
           src_ptr = src_buffer[offset_x]
         [dst_blk_y + offset_y + y_crop_blocks];
           for (i = 0; i < DCTSIZE; i++)
         for (j = 0; j < DCTSIZE; j++)
           dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
         }
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_rot_270 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
         JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
         jvirt_barray_ptr *src_coef_arrays,
         jvirt_barray_ptr *dst_coef_arrays)
 /* 270 degree rotation is equivalent to
  *   1. Horizontal mirroring;
  *   2. Transposing the image.
  * These two steps are merged into a single processing routine.
  */
 {
   JDIMENSION MCU_rows, comp_height, dst_blk_x, dst_blk_y;
   JDIMENSION x_crop_blocks, y_crop_blocks;
   int ci, i, j, offset_x, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   /* Because of the horizontal mirror step, we can't process partial iMCUs
    * at the (output) bottom edge properly.  They just get transposed and
    * not mirrored.
    */
   MCU_rows = srcinfo->output_width /
     (dstinfo->max_v_samp_factor * dstinfo->min_DCT_v_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_height = MCU_rows * compptr->v_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks;
          dst_blk_x += compptr->h_samp_factor) {
       src_buffer = (*srcinfo->mem->access_virt_barray)
         ((j_common_ptr) srcinfo, src_coef_arrays[ci],
          dst_blk_x + x_crop_blocks,
          (JDIMENSION) compptr->h_samp_factor, FALSE);
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         if (y_crop_blocks + dst_blk_y < comp_height) {
           /* Block is within the mirrorable area. */
           src_ptr = src_buffer[offset_x]
         [comp_height - y_crop_blocks - dst_blk_y - offset_y - 1];
           for (i = 0; i < DCTSIZE; i++) {
         for (j = 0; j < DCTSIZE; j++) {
           dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
           j++;
           dst_ptr[j*DCTSIZE+i] = -src_ptr[i*DCTSIZE+j];
         }
           }
         } else {
           /* Edge blocks are transposed but not mirrored. */
           src_ptr = src_buffer[offset_x]
         [dst_blk_y + offset_y + y_crop_blocks];
           for (i = 0; i < DCTSIZE; i++)
         for (j = 0; j < DCTSIZE; j++)
           dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
         }
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_rot_180 (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
         JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
         jvirt_barray_ptr *src_coef_arrays,
         jvirt_barray_ptr *dst_coef_arrays)
 /* 180 degree rotation is equivalent to
  *   1. Vertical mirroring;
  *   2. Horizontal mirroring.
  * These two steps are merged into a single processing routine.
  */
 {
   JDIMENSION MCU_cols, MCU_rows, comp_width, comp_height, dst_blk_x, dst_blk_y;
   JDIMENSION x_crop_blocks, y_crop_blocks;
   int ci, i, j, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JBLOCKROW src_row_ptr, dst_row_ptr;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   MCU_cols = srcinfo->output_width /
     (dstinfo->max_h_samp_factor * dstinfo->min_DCT_h_scaled_size);
   MCU_rows = srcinfo->output_height /
     (dstinfo->max_v_samp_factor * dstinfo->min_DCT_v_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * compptr->h_samp_factor;
     comp_height = MCU_rows * compptr->v_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       if (y_crop_blocks + dst_blk_y < comp_height) {
     /* Row is within the vertically mirrorable area. */
     src_buffer = (*srcinfo->mem->access_virt_barray)
       ((j_common_ptr) srcinfo, src_coef_arrays[ci],
        comp_height - y_crop_blocks - dst_blk_y -
        (JDIMENSION) compptr->v_samp_factor,
        (JDIMENSION) compptr->v_samp_factor, FALSE);
       } else {
     /* Bottom-edge rows are only mirrored horizontally. */
     src_buffer = (*srcinfo->mem->access_virt_barray)
       ((j_common_ptr) srcinfo, src_coef_arrays[ci],
        dst_blk_y + y_crop_blocks,
        (JDIMENSION) compptr->v_samp_factor, FALSE);
       }
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     dst_row_ptr = dst_buffer[offset_y];
     if (y_crop_blocks + dst_blk_y < comp_height) {
       /* Row is within the mirrorable area. */
       src_row_ptr = src_buffer[compptr->v_samp_factor - offset_y - 1];
       for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks; dst_blk_x++) {
         dst_ptr = dst_row_ptr[dst_blk_x];
         if (x_crop_blocks + dst_blk_x < comp_width) {
           /* Process the blocks that can be mirrored both ways. */
           src_ptr = src_row_ptr[comp_width - x_crop_blocks - dst_blk_x - 1];
           for (i = 0; i < DCTSIZE; i += 2) {
         /* For even row, negate every odd column. */
         for (j = 0; j < DCTSIZE; j += 2) {
           *dst_ptr++ = *src_ptr++;
           *dst_ptr++ = - *src_ptr++;
         }
         /* For odd row, negate every even column. */
         for (j = 0; j < DCTSIZE; j += 2) {
           *dst_ptr++ = - *src_ptr++;
           *dst_ptr++ = *src_ptr++;
         }
           }
         } else {
           /* Any remaining right-edge blocks are only mirrored vertically. */
           src_ptr = src_row_ptr[x_crop_blocks + dst_blk_x];
           for (i = 0; i < DCTSIZE; i += 2) {
         for (j = 0; j < DCTSIZE; j++)
           *dst_ptr++ = *src_ptr++;
         for (j = 0; j < DCTSIZE; j++)
           *dst_ptr++ = - *src_ptr++;
           }
         }
       }
     } else {
       /* Remaining rows are just mirrored horizontally. */
       src_row_ptr = src_buffer[offset_y];
       for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks; dst_blk_x++) {
         if (x_crop_blocks + dst_blk_x < comp_width) {
           /* Process the blocks that can be mirrored. */
           dst_ptr = dst_row_ptr[dst_blk_x];
           src_ptr = src_row_ptr[comp_width - x_crop_blocks - dst_blk_x - 1];
           for (i = 0; i < DCTSIZE2; i += 2) {
         *dst_ptr++ = *src_ptr++;
         *dst_ptr++ = - *src_ptr++;
           }
         } else {
           /* Any remaining right-edge blocks are only copied. */
           jcopy_block_row(src_row_ptr + dst_blk_x + x_crop_blocks,
                   dst_row_ptr + dst_blk_x,
                   (JDIMENSION) 1);
         }
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_transverse (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
            JDIMENSION x_crop_offset, JDIMENSION y_crop_offset,
            jvirt_barray_ptr *src_coef_arrays,
            jvirt_barray_ptr *dst_coef_arrays)
 /* Transverse transpose is equivalent to
  *   1. 180 degree rotation;
  *   2. Transposition;
  * or
  *   1. Horizontal mirroring;
  *   2. Transposition;
  *   3. Horizontal mirroring.
  * These steps are merged into a single processing routine.
  */
 {
   JDIMENSION MCU_cols, MCU_rows, comp_width, comp_height, dst_blk_x, dst_blk_y;
   JDIMENSION x_crop_blocks, y_crop_blocks;
   int ci, i, j, offset_x, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   MCU_cols = srcinfo->output_height /
     (dstinfo->max_h_samp_factor * dstinfo->min_DCT_h_scaled_size);
   MCU_rows = srcinfo->output_width /
     (dstinfo->max_v_samp_factor * dstinfo->min_DCT_v_scaled_size);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * compptr->h_samp_factor;
     comp_height = MCU_rows * compptr->v_samp_factor;
     x_crop_blocks = x_crop_offset * compptr->h_samp_factor;
     y_crop_blocks = y_crop_offset * compptr->v_samp_factor;
     for (dst_blk_y = 0; dst_blk_y < compptr->height_in_blocks;
      dst_blk_y += compptr->v_samp_factor) {
       dst_buffer = (*srcinfo->mem->access_virt_barray)
     ((j_common_ptr) srcinfo, dst_coef_arrays[ci], dst_blk_y,
      (JDIMENSION) compptr->v_samp_factor, TRUE);
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     for (dst_blk_x = 0; dst_blk_x < compptr->width_in_blocks;
          dst_blk_x += compptr->h_samp_factor) {
       if (x_crop_blocks + dst_blk_x < comp_width) {
         /* Block is within the mirrorable area. */
         src_buffer = (*srcinfo->mem->access_virt_barray)
           ((j_common_ptr) srcinfo, src_coef_arrays[ci],
            comp_width - x_crop_blocks - dst_blk_x -
            (JDIMENSION) compptr->h_samp_factor,
            (JDIMENSION) compptr->h_samp_factor, FALSE);
       } else {
         src_buffer = (*srcinfo->mem->access_virt_barray)
           ((j_common_ptr) srcinfo, src_coef_arrays[ci],
            dst_blk_x + x_crop_blocks,
            (JDIMENSION) compptr->h_samp_factor, FALSE);
       }
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         if (y_crop_blocks + dst_blk_y < comp_height) {
           if (x_crop_blocks + dst_blk_x < comp_width) {
         /* Block is within the mirrorable area. */
         src_ptr = src_buffer[compptr->h_samp_factor - offset_x - 1]
           [comp_height - y_crop_blocks - dst_blk_y - offset_y - 1];
         for (i = 0; i < DCTSIZE; i++) {
           for (j = 0; j < DCTSIZE; j++) {
             dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
             j++;
             dst_ptr[j*DCTSIZE+i] = -src_ptr[i*DCTSIZE+j];
           }
           i++;
           for (j = 0; j < DCTSIZE; j++) {
             dst_ptr[j*DCTSIZE+i] = -src_ptr[i*DCTSIZE+j];
             j++;
             dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
           }
         }
           } else {
         /* Right-edge blocks are mirrored in y only */
         src_ptr = src_buffer[offset_x]
           [comp_height - y_crop_blocks - dst_blk_y - offset_y - 1];
         for (i = 0; i < DCTSIZE; i++) {
           for (j = 0; j < DCTSIZE; j++) {
             dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
             j++;
             dst_ptr[j*DCTSIZE+i] = -src_ptr[i*DCTSIZE+j];
           }
         }
           }
         } else {
           if (x_crop_blocks + dst_blk_x < comp_width) {
         /* Bottom-edge blocks are mirrored in x only */
         src_ptr = src_buffer[compptr->h_samp_factor - offset_x - 1]
           [dst_blk_y + offset_y + y_crop_blocks];
         for (i = 0; i < DCTSIZE; i++) {
           for (j = 0; j < DCTSIZE; j++)
             dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
           i++;
           for (j = 0; j < DCTSIZE; j++)
             dst_ptr[j*DCTSIZE+i] = -src_ptr[i*DCTSIZE+j];
         }
           } else {
         /* At lower right corner, just transpose, no mirroring */
         src_ptr = src_buffer[offset_x]
           [dst_blk_y + offset_y + y_crop_blocks];
         for (i = 0; i < DCTSIZE; i++)
           for (j = 0; j < DCTSIZE; j++)
             dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
           }
         }
       }
     }
       }
     }
   }
 }
 
 
 /* Parse an unsigned integer: subroutine for jtransform_parse_crop_spec.
  * Returns TRUE if valid integer found, FALSE if not.
  * *strptr is advanced over the digit string, and *result is set to its value.
  */
 
 LOCAL(boolean)
 jt_read_integer (const char ** strptr, JDIMENSION * result)
 {
   const char * ptr = *strptr;
   JDIMENSION val = 0;
 
   for (; isdigit(*ptr); ptr++) {
     val = val * 10 + (JDIMENSION) (*ptr - '0');
   }
   *result = val;
   if (ptr == *strptr)
     return FALSE;       /* oops, no digits */
   *strptr = ptr;
   return TRUE;
 }
 
 
 /* Parse a crop specification (written in X11 geometry style).
  * The routine returns TRUE if the spec string is valid, FALSE if not.
  *
  * The crop spec string should have the format
  *  <width>[f]x<height>[f]{+-}<xoffset>{+-}<yoffset>
  * where width, height, xoffset, and yoffset are unsigned integers.
  * Each of the elements can be omitted to indicate a default value.
  * (A weakness of this style is that it is not possible to omit xoffset
  * while specifying yoffset, since they look alike.)
  *
  * This code is loosely based on XParseGeometry from the X11 distribution.
  */
 
 GLOBAL(boolean)
 jtransform_parse_crop_spec (jpeg_transform_info *info, const char *spec)
 {
   info->crop = FALSE;
   info->crop_width_set = JCROP_UNSET;
   info->crop_height_set = JCROP_UNSET;
   info->crop_xoffset_set = JCROP_UNSET;
   info->crop_yoffset_set = JCROP_UNSET;
 
   if (isdigit(*spec)) {
     /* fetch width */
     if (! jt_read_integer(&spec, &info->crop_width))
       return FALSE;
     if (*spec == 'f' || *spec == 'F') {
       spec++;
       info->crop_width_set = JCROP_FORCE;
     } else
       info->crop_width_set = JCROP_POS;
   }
   if (*spec == 'x' || *spec == 'X') {
     /* fetch height */
     spec++;
     if (! jt_read_integer(&spec, &info->crop_height))
       return FALSE;
     if (*spec == 'f' || *spec == 'F') {
       spec++;
       info->crop_height_set = JCROP_FORCE;
     } else
       info->crop_height_set = JCROP_POS;
   }
   if (*spec == '+' || *spec == '-') {
     /* fetch xoffset */
     info->crop_xoffset_set = (*spec == '-') ? JCROP_NEG : JCROP_POS;
     spec++;
     if (! jt_read_integer(&spec, &info->crop_xoffset))
       return FALSE;
   }
   if (*spec == '+' || *spec == '-') {
     /* fetch yoffset */
     info->crop_yoffset_set = (*spec == '-') ? JCROP_NEG : JCROP_POS;
     spec++;
     if (! jt_read_integer(&spec, &info->crop_yoffset))
       return FALSE;
   }
   /* We had better have gotten to the end of the string. */
   if (*spec != '\0')
     return FALSE;
   info->crop = TRUE;
   return TRUE;
 }
 
 
 /* Trim off any partial iMCUs on the indicated destination edge */
 
 LOCAL(void)
 trim_right_edge (jpeg_transform_info *info, JDIMENSION full_width)
 {
   JDIMENSION MCU_cols;
 
   MCU_cols = info->output_width / info->iMCU_sample_width;
   if (MCU_cols > 0 && info->x_crop_offset + MCU_cols ==
       full_width / info->iMCU_sample_width)
     info->output_width = MCU_cols * info->iMCU_sample_width;
 }
 
 LOCAL(void)
 trim_bottom_edge (jpeg_transform_info *info, JDIMENSION full_height)
 {
   JDIMENSION MCU_rows;
 
   MCU_rows = info->output_height / info->iMCU_sample_height;
   if (MCU_rows > 0 && info->y_crop_offset + MCU_rows ==
       full_height / info->iMCU_sample_height)
     info->output_height = MCU_rows * info->iMCU_sample_height;
 }
 
 
 /* Request any required workspace.
  *
  * This routine figures out the size that the output image will be
  * (which implies that all the transform parameters must be set before
  * it is called).
  *
  * We allocate the workspace virtual arrays from the source decompression
  * object, so that all the arrays (both the original data and the workspace)
  * will be taken into account while making memory management decisions.
  * Hence, this routine must be called after jpeg_read_header (which reads
  * the image dimensions) and before jpeg_read_coefficients (which realizes
  * the source's virtual arrays).
  *
  * This function returns FALSE right away if -perfect is given
  * and transformation is not perfect.  Otherwise returns TRUE.
  */
 
 GLOBAL(boolean)
 jtransform_request_workspace (j_decompress_ptr srcinfo,
                   jpeg_transform_info *info)
 {
   jvirt_barray_ptr *coef_arrays;
   boolean need_workspace, transpose_it;
   jpeg_component_info *compptr;
   JDIMENSION xoffset, yoffset;
   JDIMENSION width_in_iMCUs, height_in_iMCUs;
   JDIMENSION width_in_blocks, height_in_blocks;
   int ci, h_samp_factor, v_samp_factor;
 
   /* Determine number of components in output image */
   if (info->force_grayscale &&
       srcinfo->jpeg_color_space == JCS_YCbCr &&
       srcinfo->num_components == 3)
     /* We'll only process the first component */
     info->num_components = 1;
   else
     /* Process all the components */
     info->num_components = srcinfo->num_components;
 
   /* Compute output image dimensions and related values. */
   jpeg_core_output_dimensions(srcinfo);
 
   /* Return right away if -perfect is given and transformation is not perfect.
    */
   if (info->perfect) {
     if (info->num_components == 1) {
       if (!jtransform_perfect_transform(srcinfo->output_width,
       srcinfo->output_height,
       srcinfo->min_DCT_h_scaled_size,
       srcinfo->min_DCT_v_scaled_size,
       info->transform))
     return FALSE;
     } else {
       if (!jtransform_perfect_transform(srcinfo->output_width,
       srcinfo->output_height,
       srcinfo->max_h_samp_factor * srcinfo->min_DCT_h_scaled_size,
       srcinfo->max_v_samp_factor * srcinfo->min_DCT_v_scaled_size,
       info->transform))
     return FALSE;
     }
   }
 
   /* If there is only one output component, force the iMCU size to be 1;
    * else use the source iMCU size.  (This allows us to do the right thing
    * when reducing color to grayscale, and also provides a handy way of
    * cleaning up "funny" grayscale images whose sampling factors are not 1x1.)
    */
   switch (info->transform) {
   case JXFORM_TRANSPOSE:
   case JXFORM_TRANSVERSE:
   case JXFORM_ROT_90:
   case JXFORM_ROT_270:
     info->output_width = srcinfo->output_height;
     info->output_height = srcinfo->output_width;
     if (info->num_components == 1) {
       info->iMCU_sample_width = srcinfo->min_DCT_v_scaled_size;
       info->iMCU_sample_height = srcinfo->min_DCT_h_scaled_size;
     } else {
       info->iMCU_sample_width =
     srcinfo->max_v_samp_factor * srcinfo->min_DCT_v_scaled_size;
       info->iMCU_sample_height =
     srcinfo->max_h_samp_factor * srcinfo->min_DCT_h_scaled_size;
     }
     break;
   default:
     info->output_width = srcinfo->output_width;
     info->output_height = srcinfo->output_height;
     if (info->num_components == 1) {
       info->iMCU_sample_width = srcinfo->min_DCT_h_scaled_size;
       info->iMCU_sample_height = srcinfo->min_DCT_v_scaled_size;
     } else {
       info->iMCU_sample_width =
     srcinfo->max_h_samp_factor * srcinfo->min_DCT_h_scaled_size;
       info->iMCU_sample_height =
     srcinfo->max_v_samp_factor * srcinfo->min_DCT_v_scaled_size;
     }
     break;
   }
 
   /* If cropping has been requested, compute the crop area's position and
    * dimensions, ensuring that its upper left corner falls at an iMCU boundary.
    */
   if (info->crop) {
     /* Insert default values for unset crop parameters */
     if (info->crop_xoffset_set == JCROP_UNSET)
       info->crop_xoffset = 0;   /* default to +0 */
     if (info->crop_yoffset_set == JCROP_UNSET)
       info->crop_yoffset = 0;   /* default to +0 */
     if (info->crop_xoffset >= info->output_width ||
     info->crop_yoffset >= info->output_height)
       ERREXIT(srcinfo, JERR_BAD_CROP_SPEC);
     if (info->crop_width_set == JCROP_UNSET)
       info->crop_width = info->output_width - info->crop_xoffset;
     if (info->crop_height_set == JCROP_UNSET)
       info->crop_height = info->output_height - info->crop_yoffset;
     /* Ensure parameters are valid */
     if (info->crop_width <= 0 || info->crop_width > info->output_width ||
     info->crop_height <= 0 || info->crop_height > info->output_height ||
     info->crop_xoffset > info->output_width - info->crop_width ||
     info->crop_yoffset > info->output_height - info->crop_height)
       ERREXIT(srcinfo, JERR_BAD_CROP_SPEC);
     /* Convert negative crop offsets into regular offsets */
     if (info->crop_xoffset_set == JCROP_NEG)
       xoffset = info->output_width - info->crop_width - info->crop_xoffset;
     else
       xoffset = info->crop_xoffset;
     if (info->crop_yoffset_set == JCROP_NEG)
       yoffset = info->output_height - info->crop_height - info->crop_yoffset;
     else
       yoffset = info->crop_yoffset;
     /* Now adjust so that upper left corner falls at an iMCU boundary */
     if (info->crop_width_set == JCROP_FORCE)
       info->output_width = info->crop_width;
     else
       info->output_width =
         info->crop_width + (xoffset % info->iMCU_sample_width);
     if (info->crop_height_set == JCROP_FORCE)
       info->output_height = info->crop_height;
     else
       info->output_height =
         info->crop_height + (yoffset % info->iMCU_sample_height);
     /* Save x/y offsets measured in iMCUs */
     info->x_crop_offset = xoffset / info->iMCU_sample_width;
     info->y_crop_offset = yoffset / info->iMCU_sample_height;
   } else {
     info->x_crop_offset = 0;
     info->y_crop_offset = 0;
   }
 
   /* Figure out whether we need workspace arrays,
    * and if so whether they are transposed relative to the source.
    */
   need_workspace = FALSE;
   transpose_it = FALSE;
   switch (info->transform) {
   case JXFORM_NONE:
     if (info->x_crop_offset != 0 || info->y_crop_offset != 0)
       need_workspace = TRUE;
     /* No workspace needed if neither cropping nor transforming */
     break;
   case JXFORM_FLIP_H:
     if (info->trim)
       trim_right_edge(info, srcinfo->output_width);
     if (info->y_crop_offset != 0)
       need_workspace = TRUE;
     /* do_flip_h_no_crop doesn't need a workspace array */
     break;
   case JXFORM_FLIP_V:
     if (info->trim)
       trim_bottom_edge(info, srcinfo->output_height);
     /* Need workspace arrays having same dimensions as source image. */
     need_workspace = TRUE;
     break;
   case JXFORM_TRANSPOSE:
     /* transpose does NOT have to trim anything */
     /* Need workspace arrays having transposed dimensions. */
     need_workspace = TRUE;
     transpose_it = TRUE;
     break;
   case JXFORM_TRANSVERSE:
     if (info->trim) {
       trim_right_edge(info, srcinfo->output_height);
       trim_bottom_edge(info, srcinfo->output_width);
     }
     /* Need workspace arrays having transposed dimensions. */
     need_workspace = TRUE;
     transpose_it = TRUE;
     break;
   case JXFORM_ROT_90:
     if (info->trim)
       trim_right_edge(info, srcinfo->output_height);
     /* Need workspace arrays having transposed dimensions. */
     need_workspace = TRUE;
     transpose_it = TRUE;
     break;
   case JXFORM_ROT_180:
     if (info->trim) {
       trim_right_edge(info, srcinfo->output_width);
       trim_bottom_edge(info, srcinfo->output_height);
     }
     /* Need workspace arrays having same dimensions as source image. */
     need_workspace = TRUE;
     break;
   case JXFORM_ROT_270:
     if (info->trim)
       trim_bottom_edge(info, srcinfo->output_width);
     /* Need workspace arrays having transposed dimensions. */
     need_workspace = TRUE;
     transpose_it = TRUE;
     break;
   }
 
   /* Allocate workspace if needed.
    * Note that we allocate arrays padded out to the next iMCU boundary,
    * so that transform routines need not worry about missing edge blocks.
    */
   if (need_workspace) {
     coef_arrays = (jvirt_barray_ptr *)
       (*srcinfo->mem->alloc_small) ((j_common_ptr) srcinfo, JPOOL_IMAGE,
         SIZEOF(jvirt_barray_ptr) * info->num_components);
     width_in_iMCUs = (JDIMENSION)
       jdiv_round_up((long) info->output_width,
             (long) info->iMCU_sample_width);
     height_in_iMCUs = (JDIMENSION)
       jdiv_round_up((long) info->output_height,
             (long) info->iMCU_sample_height);
     for (ci = 0; ci < info->num_components; ci++) {
       compptr = srcinfo->comp_info + ci;
       if (info->num_components == 1) {
     /* we're going to force samp factors to 1x1 in this case */
     h_samp_factor = v_samp_factor = 1;
       } else if (transpose_it) {
     h_samp_factor = compptr->v_samp_factor;
     v_samp_factor = compptr->h_samp_factor;
       } else {
     h_samp_factor = compptr->h_samp_factor;
     v_samp_factor = compptr->v_samp_factor;
       }
       width_in_blocks = width_in_iMCUs * h_samp_factor;
       height_in_blocks = height_in_iMCUs * v_samp_factor;
       coef_arrays[ci] = (*srcinfo->mem->request_virt_barray)
     ((j_common_ptr) srcinfo, JPOOL_IMAGE, FALSE,
      width_in_blocks, height_in_blocks, (JDIMENSION) v_samp_factor);
     }
     info->workspace_coef_arrays = coef_arrays;
   } else
     info->workspace_coef_arrays = NULL;
 
   return TRUE;
 }
 
 
 /* Transpose destination image parameters */
 
 LOCAL(void)
 transpose_critical_parameters (j_compress_ptr dstinfo)
 {
   int tblno, i, j, ci, itemp;
   jpeg_component_info *compptr;
   JQUANT_TBL *qtblptr;
   JDIMENSION jtemp;
   UINT16 qtemp;
 
   /* Transpose image dimensions */
   jtemp = dstinfo->image_width;
   dstinfo->image_width = dstinfo->image_height;
   dstinfo->image_height = jtemp;
   itemp = dstinfo->min_DCT_h_scaled_size;
   dstinfo->min_DCT_h_scaled_size = dstinfo->min_DCT_v_scaled_size;
   dstinfo->min_DCT_v_scaled_size = itemp;
 
   /* Transpose sampling factors */
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     itemp = compptr->h_samp_factor;
     compptr->h_samp_factor = compptr->v_samp_factor;
     compptr->v_samp_factor = itemp;
   }
 
   /* Transpose quantization tables */
   for (tblno = 0; tblno < NUM_QUANT_TBLS; tblno++) {
     qtblptr = dstinfo->quant_tbl_ptrs[tblno];
     if (qtblptr != NULL) {
       for (i = 0; i < DCTSIZE; i++) {
     for (j = 0; j < i; j++) {
       qtemp = qtblptr->quantval[i*DCTSIZE+j];
       qtblptr->quantval[i*DCTSIZE+j] = qtblptr->quantval[j*DCTSIZE+i];
       qtblptr->quantval[j*DCTSIZE+i] = qtemp;
     }
       }
     }
   }
 }
 
 
 /* Adjust Exif image parameters.
  *
  * We try to adjust the Tags ExifImageWidth and ExifImageHeight if possible.
  */
 
 LOCAL(void)
 adjust_exif_parameters (JOCTET FAR * data, unsigned int length,
             JDIMENSION new_width, JDIMENSION new_height)
 {
   boolean is_motorola; /* Flag for byte order */
   unsigned int number_of_tags, tagnum;
   unsigned int firstoffset, offset;
   JDIMENSION new_value;
 
   if (length < 12) return; /* Length of an IFD entry */
 
   /* Discover byte order */
   if (GETJOCTET(data[0]) == 0x49 && GETJOCTET(data[1]) == 0x49)
     is_motorola = FALSE;
   else if (GETJOCTET(data[0]) == 0x4D && GETJOCTET(data[1]) == 0x4D)
     is_motorola = TRUE;
   else
     return;
 
   /* Check Tag Mark */
   if (is_motorola) {
     if (GETJOCTET(data[2]) != 0) return;
     if (GETJOCTET(data[3]) != 0x2A) return;
   } else {
     if (GETJOCTET(data[3]) != 0) return;
     if (GETJOCTET(data[2]) != 0x2A) return;
   }
 
   /* Get first IFD offset (offset to IFD0) */
   if (is_motorola) {
     if (GETJOCTET(data[4]) != 0) return;
     if (GETJOCTET(data[5]) != 0) return;
     firstoffset = GETJOCTET(data[6]);
     firstoffset <<= 8;
     firstoffset += GETJOCTET(data[7]);
   } else {
     if (GETJOCTET(data[7]) != 0) return;
     if (GETJOCTET(data[6]) != 0) return;
     firstoffset = GETJOCTET(data[5]);
     firstoffset <<= 8;
     firstoffset += GETJOCTET(data[4]);
   }
   if (firstoffset > length - 2) return; /* check end of data segment */
 
   /* Get the number of directory entries contained in this IFD */
   if (is_motorola) {
     number_of_tags = GETJOCTET(data[firstoffset]);
     number_of_tags <<= 8;
     number_of_tags += GETJOCTET(data[firstoffset+1]);
   } else {
     number_of_tags = GETJOCTET(data[firstoffset+1]);
     number_of_tags <<= 8;
     number_of_tags += GETJOCTET(data[firstoffset]);
   }
   if (number_of_tags == 0) return;
   firstoffset += 2;
 
   /* Search for ExifSubIFD offset Tag in IFD0 */
   for (;;) {
     if (firstoffset > length - 12) return; /* check end of data segment */
     /* Get Tag number */
     if (is_motorola) {
       tagnum = GETJOCTET(data[firstoffset]);
       tagnum <<= 8;
       tagnum += GETJOCTET(data[firstoffset+1]);
     } else {
       tagnum = GETJOCTET(data[firstoffset+1]);
       tagnum <<= 8;
       tagnum += GETJOCTET(data[firstoffset]);
     }
     if (tagnum == 0x8769) break; /* found ExifSubIFD offset Tag */
     if (--number_of_tags == 0) return;
     firstoffset += 12;
   }
 
   /* Get the ExifSubIFD offset */
   if (is_motorola) {
     if (GETJOCTET(data[firstoffset+8]) != 0) return;
     if (GETJOCTET(data[firstoffset+9]) != 0) return;
     offset = GETJOCTET(data[firstoffset+10]);
     offset <<= 8;
     offset += GETJOCTET(data[firstoffset+11]);
   } else {
     if (GETJOCTET(data[firstoffset+11]) != 0) return;
     if (GETJOCTET(data[firstoffset+10]) != 0) return;
     offset = GETJOCTET(data[firstoffset+9]);
     offset <<= 8;
     offset += GETJOCTET(data[firstoffset+8]);
   }
   if (offset > length - 2) return; /* check end of data segment */
 
   /* Get the number of directory entries contained in this SubIFD */
   if (is_motorola) {
     number_of_tags = GETJOCTET(data[offset]);
     number_of_tags <<= 8;
     number_of_tags += GETJOCTET(data[offset+1]);
   } else {
     number_of_tags = GETJOCTET(data[offset+1]);
     number_of_tags <<= 8;
     number_of_tags += GETJOCTET(data[offset]);
   }
   if (number_of_tags < 2) return;
   offset += 2;
 
   /* Search for ExifImageWidth and ExifImageHeight Tags in this SubIFD */
   do {
     if (offset > length - 12) return; /* check end of data segment */
     /* Get Tag number */
     if (is_motorola) {
       tagnum = GETJOCTET(data[offset]);
       tagnum <<= 8;
       tagnum += GETJOCTET(data[offset+1]);
     } else {
       tagnum = GETJOCTET(data[offset+1]);
       tagnum <<= 8;
       tagnum += GETJOCTET(data[offset]);
     }
     if (tagnum == 0xA002 || tagnum == 0xA003) {
       if (tagnum == 0xA002)
     new_value = new_width; /* ExifImageWidth Tag */
       else
     new_value = new_height; /* ExifImageHeight Tag */
       if (is_motorola) {
     data[offset+2] = 0; /* Format = unsigned long (4 octets) */
     data[offset+3] = 4;
     data[offset+4] = 0; /* Number Of Components = 1 */
     data[offset+5] = 0;
     data[offset+6] = 0;
     data[offset+7] = 1;
     data[offset+8] = 0;
     data[offset+9] = 0;
     data[offset+10] = (JOCTET)((new_value >> 8) & 0xFF);
     data[offset+11] = (JOCTET)(new_value & 0xFF);
       } else {
     data[offset+2] = 4; /* Format = unsigned long (4 octets) */
     data[offset+3] = 0;
     data[offset+4] = 1; /* Number Of Components = 1 */
     data[offset+5] = 0;
     data[offset+6] = 0;
     data[offset+7] = 0;
     data[offset+8] = (JOCTET)(new_value & 0xFF);
     data[offset+9] = (JOCTET)((new_value >> 8) & 0xFF);
     data[offset+10] = 0;
     data[offset+11] = 0;
       }
     }
     offset += 12;
   } while (--number_of_tags);
 }
 
 
 /* Adjust output image parameters as needed.
  *
  * This must be called after jpeg_copy_critical_parameters()
  * and before jpeg_write_coefficients().
  *
  * The return value is the set of virtual coefficient arrays to be written
  * (either the ones allocated by jtransform_request_workspace, or the
  * original source data arrays).  The caller will need to pass this value
  * to jpeg_write_coefficients().
  */
 
 GLOBAL(jvirt_barray_ptr *)
 jtransform_adjust_parameters (j_decompress_ptr srcinfo,
                   j_compress_ptr dstinfo,
                   jvirt_barray_ptr *src_coef_arrays,
                   jpeg_transform_info *info)
 {
   /* If force-to-grayscale is requested, adjust destination parameters */
   if (info->force_grayscale) {
     /* First, ensure we have YCbCr or grayscale data, and that the source's
      * Y channel is full resolution.  (No reasonable person would make Y
      * be less than full resolution, so actually coping with that case
      * isn't worth extra code space.  But we check it to avoid crashing.)
      */
     if (((dstinfo->jpeg_color_space == JCS_YCbCr &&
       dstinfo->num_components == 3) ||
      (dstinfo->jpeg_color_space == JCS_GRAYSCALE &&
       dstinfo->num_components == 1)) &&
     srcinfo->comp_info[0].h_samp_factor == srcinfo->max_h_samp_factor &&
     srcinfo->comp_info[0].v_samp_factor == srcinfo->max_v_samp_factor) {
       /* We use jpeg_set_colorspace to make sure subsidiary settings get fixed
        * properly.  Among other things, it sets the target h_samp_factor &
        * v_samp_factor to 1, which typically won't match the source.
        * We have to preserve the source's quantization table number, however.
        */
       int sv_quant_tbl_no = dstinfo->comp_info[0].quant_tbl_no;
       jpeg_set_colorspace(dstinfo, JCS_GRAYSCALE);
       dstinfo->comp_info[0].quant_tbl_no = sv_quant_tbl_no;
     } else {
       /* Sorry, can't do it */
       ERREXIT(dstinfo, JERR_CONVERSION_NOTIMPL);
     }
   } else if (info->num_components == 1) {
     /* For a single-component source, we force the destination sampling factors
      * to 1x1, with or without force_grayscale.  This is useful because some
      * decoders choke on grayscale images with other sampling factors.
      */
     dstinfo->comp_info[0].h_samp_factor = 1;
     dstinfo->comp_info[0].v_samp_factor = 1;
   }
 
   /* Correct the destination's image dimensions as necessary
    * for rotate/flip, resize, and crop operations.
    */
   dstinfo->jpeg_width = info->output_width;
   dstinfo->jpeg_height = info->output_height;
 
   /* Transpose destination image parameters */
   switch (info->transform) {
   case JXFORM_TRANSPOSE:
   case JXFORM_TRANSVERSE:
   case JXFORM_ROT_90:
   case JXFORM_ROT_270:
     transpose_critical_parameters(dstinfo);
     break;
   default:
     break;
   }
 
   /* Adjust Exif properties */
   if (srcinfo->marker_list != NULL &&
       srcinfo->marker_list->marker == JPEG_APP0+1 &&
       srcinfo->marker_list->data_length >= 6 &&
       GETJOCTET(srcinfo->marker_list->data[0]) == 0x45 &&
       GETJOCTET(srcinfo->marker_list->data[1]) == 0x78 &&
       GETJOCTET(srcinfo->marker_list->data[2]) == 0x69 &&
       GETJOCTET(srcinfo->marker_list->data[3]) == 0x66 &&
       GETJOCTET(srcinfo->marker_list->data[4]) == 0 &&
       GETJOCTET(srcinfo->marker_list->data[5]) == 0) {
     /* Suppress output of JFIF marker */
     dstinfo->write_JFIF_header = FALSE;
     /* Adjust Exif image parameters */
     if (dstinfo->jpeg_width != srcinfo->image_width ||
     dstinfo->jpeg_height != srcinfo->image_height)
       /* Align data segment to start of TIFF structure for parsing */
       adjust_exif_parameters(srcinfo->marker_list->data + 6,
     srcinfo->marker_list->data_length - 6,
     dstinfo->jpeg_width, dstinfo->jpeg_height);
   }
 
   /* Return the appropriate output data set */
   if (info->workspace_coef_arrays != NULL)
     return info->workspace_coef_arrays;
   return src_coef_arrays;
 }
 
 
 /* Execute the actual transformation, if any.
  *
  * This must be called *after* jpeg_write_coefficients, because it depends
  * on jpeg_write_coefficients to have computed subsidiary values such as
  * the per-component width and height fields in the destination object.
  *
  * Note that some transformations will modify the source data arrays!
  */
 
 GLOBAL(void)
 jtransform_execute_transform (j_decompress_ptr srcinfo,
                   j_compress_ptr dstinfo,
                   jvirt_barray_ptr *src_coef_arrays,
                   jpeg_transform_info *info)
 {
   jvirt_barray_ptr *dst_coef_arrays = info->workspace_coef_arrays;
 
   /* Note: conditions tested here should match those in switch statement
    * in jtransform_request_workspace()
    */
   switch (info->transform) {
   case JXFORM_NONE:
     if (info->x_crop_offset != 0 || info->y_crop_offset != 0)
       do_crop(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
           src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_FLIP_H:
     if (info->y_crop_offset != 0)
       do_flip_h(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
         src_coef_arrays, dst_coef_arrays);
     else
       do_flip_h_no_crop(srcinfo, dstinfo, info->x_crop_offset,
             src_coef_arrays);
     break;
   case JXFORM_FLIP_V:
     do_flip_v(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
           src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_TRANSPOSE:
     do_transpose(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
          src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_TRANSVERSE:
     do_transverse(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
           src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_ROT_90:
     do_rot_90(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
           src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_ROT_180:
     do_rot_180(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
            src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_ROT_270:
     do_rot_270(srcinfo, dstinfo, info->x_crop_offset, info->y_crop_offset,
            src_coef_arrays, dst_coef_arrays);
     break;
   }
 }
 
 /* jtransform_perfect_transform
  *
  * Determine whether lossless transformation is perfectly
  * possible for a specified image and transformation.
  *
  * Inputs:
  *   image_width, image_height: source image dimensions.
  *   MCU_width, MCU_height: pixel dimensions of MCU.
  *   transform: transformation identifier.
  * Parameter sources from initialized jpeg_struct
  * (after reading source header):
  *   image_width = cinfo.image_width
  *   image_height = cinfo.image_height
  *   MCU_width = cinfo.max_h_samp_factor * cinfo.block_size
  *   MCU_height = cinfo.max_v_samp_factor * cinfo.block_size
  * Result:
  *   TRUE = perfect transformation possible
  *   FALSE = perfect transformation not possible
  *           (may use custom action then)
  */
 
 GLOBAL(boolean)
 jtransform_perfect_transform(JDIMENSION image_width, JDIMENSION image_height,
                  int MCU_width, int MCU_height,
                  JXFORM_CODE transform)
 {
   boolean result = TRUE; /* initialize TRUE */
 
   switch (transform) {
   case JXFORM_FLIP_H:
   case JXFORM_ROT_270:
     if (image_width % (JDIMENSION) MCU_width)
       result = FALSE;
     break;
   case JXFORM_FLIP_V:
   case JXFORM_ROT_90:
     if (image_height % (JDIMENSION) MCU_height)
       result = FALSE;
     break;
   case JXFORM_TRANSVERSE:
   case JXFORM_ROT_180:
     if (image_width % (JDIMENSION) MCU_width)
       result = FALSE;
     if (image_height % (JDIMENSION) MCU_height)
       result = FALSE;
     break;
   default:
     break;
   }
 
   return result;
 }
 
 #endif /* TRANSFORMS_SUPPORTED */
 
 
 /* Setup decompression object to save desired markers in memory.
  * This must be called before jpeg_read_header() to have the desired effect.
  */
 
 GLOBAL(void)
 jcopy_markers_setup (j_decompress_ptr srcinfo, JCOPY_OPTION option)
 {
 #ifdef SAVE_MARKERS_SUPPORTED
   int m;
 
   /* Save comments except under NONE option */
   if (option != JCOPYOPT_NONE) {
     jpeg_save_markers(srcinfo, JPEG_COM, 0xFFFF);
   }
   /* Save all types of APPn markers iff ALL option */
   if (option == JCOPYOPT_ALL) {
     for (m = 0; m < 16; m++)
       jpeg_save_markers(srcinfo, JPEG_APP0 + m, 0xFFFF);
   }
 #endif /* SAVE_MARKERS_SUPPORTED */
 }
 
 /* Copy markers saved in the given source object to the destination object.
  * This should be called just after jpeg_start_compress() or
  * jpeg_write_coefficients().
  * Note that those routines will have written the SOI, and also the
  * JFIF APP0 or Adobe APP14 markers if selected.
  */
 
 GLOBAL(void)
 jcopy_markers_execute (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
                JCOPY_OPTION option)
 {
   jpeg_saved_marker_ptr marker;
 
   /* In the current implementation, we don't actually need to examine the
    * option flag here; we just copy everything that got saved.
    * But to avoid confusion, we do not output JFIF and Adobe APP14 markers
    * if the encoder library already wrote one.
    */
   for (marker = srcinfo->marker_list; marker != NULL; marker = marker->next) {
     if (dstinfo->write_JFIF_header &&
     marker->marker == JPEG_APP0 &&
     marker->data_length >= 5 &&
     GETJOCTET(marker->data[0]) == 0x4A &&
     GETJOCTET(marker->data[1]) == 0x46 &&
     GETJOCTET(marker->data[2]) == 0x49 &&
     GETJOCTET(marker->data[3]) == 0x46 &&
     GETJOCTET(marker->data[4]) == 0)
       continue;         /* reject duplicate JFIF */
     if (dstinfo->write_Adobe_marker &&
     marker->marker == JPEG_APP0+14 &&
     marker->data_length >= 5 &&
     GETJOCTET(marker->data[0]) == 0x41 &&
     GETJOCTET(marker->data[1]) == 0x64 &&
     GETJOCTET(marker->data[2]) == 0x6F &&
     GETJOCTET(marker->data[3]) == 0x62 &&
     GETJOCTET(marker->data[4]) == 0x65)
       continue;         /* reject duplicate Adobe */
 #ifdef NEED_FAR_POINTERS
     /* We could use jpeg_write_marker if the data weren't FAR... */
     {
       unsigned int i;
       jpeg_write_m_header(dstinfo, marker->marker, marker->data_length);
       for (i = 0; i < marker->data_length; i++)
     jpeg_write_m_byte(dstinfo, marker->data[i]);
     }
 #else
     jpeg_write_marker(dstinfo, marker->marker,
               marker->data, marker->data_length);
 #endif
   }
 }