File indexing completed on 2025-01-19 03:55:52

 /*
  * transupp.c
  *
  * SPDX-FileCopyrightText: 1997, Thomas G. Lane.
  * 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 */
 
 
 #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.
  *
  * 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.
  *
  * 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. 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.
  * Notes 2,3,4 boil down to this: generally we should use the destination's
  * dimensions and ignore the source's.
  */
 
 
 LOCAL(void)
 do_flip_h (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
        jvirt_barray_ptr *src_coef_arrays)
 /* Horizontal flip; done in-place, so no separate dest array is required */
 {
   JDIMENSION MCU_cols, comp_width, blk_x, blk_y;
   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 = dstinfo->image_width / (dstinfo->max_h_samp_factor * DCTSIZE);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * 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++) {
     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;
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_flip_v (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
        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;
   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 = dstinfo->image_height / (dstinfo->max_v_samp_factor * DCTSIZE);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_height = MCU_rows * 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 (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 - 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,
        (JDIMENSION) compptr->v_samp_factor, FALSE);
       }
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     if (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];
       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], dst_buffer[offset_y],
               compptr->width_in_blocks);
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_transpose (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
           jvirt_barray_ptr *src_coef_arrays,
           jvirt_barray_ptr *dst_coef_arrays)
 /* Transpose source into destination */
 {
   JDIMENSION dst_blk_x, dst_blk_y;
   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;
     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,
          (JDIMENSION) compptr->h_samp_factor, FALSE);
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         src_ptr = src_buffer[offset_x][dst_blk_y + offset_y];
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         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,
        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;
   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 = dstinfo->image_width / (dstinfo->max_h_samp_factor * DCTSIZE);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_width = MCU_cols * compptr->h_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,
          (JDIMENSION) compptr->h_samp_factor, FALSE);
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         src_ptr = src_buffer[offset_x][dst_blk_y + offset_y];
         if (dst_blk_x < comp_width) {
           /* Block is within the mirrorable area. */
           dst_ptr = dst_buffer[offset_y]
         [comp_width - dst_blk_x - offset_x - 1];
           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. */
           dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
           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,
         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;
   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 = dstinfo->image_height / (dstinfo->max_v_samp_factor * DCTSIZE);
 
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     compptr = dstinfo->comp_info + ci;
     comp_height = MCU_rows * 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,
          (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 (dst_blk_y < comp_height) {
           /* Block is within the mirrorable area. */
           src_ptr = src_buffer[offset_x]
         [comp_height - 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];
           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,
         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;
   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 = dstinfo->image_width / (dstinfo->max_h_samp_factor * DCTSIZE);
   MCU_rows = dstinfo->image_height / (dstinfo->max_v_samp_factor * DCTSIZE);
 
   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;
     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 (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 - 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,
        (JDIMENSION) compptr->v_samp_factor, FALSE);
       }
       for (offset_y = 0; offset_y < compptr->v_samp_factor; offset_y++) {
     if (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];
       /* Process the blocks that can be mirrored both ways. */
       for (dst_blk_x = 0; dst_blk_x < comp_width; dst_blk_x++) {
         dst_ptr = dst_row_ptr[dst_blk_x];
         src_ptr = src_row_ptr[comp_width - 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++;
           }
         }
       }
       /* Any remaining right-edge blocks are only mirrored vertically. */
       for (; 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) {
           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. */
       dst_row_ptr = dst_buffer[offset_y];
       src_row_ptr = src_buffer[offset_y];
       /* Process the blocks that can be mirrored. */
       for (dst_blk_x = 0; dst_blk_x < comp_width; dst_blk_x++) {
         dst_ptr = dst_row_ptr[dst_blk_x];
         src_ptr = src_row_ptr[comp_width - dst_blk_x - 1];
         for (i = 0; i < DCTSIZE2; i += 2) {
           *dst_ptr++ = *src_ptr++;
           *dst_ptr++ = - *src_ptr++;
         }
       }
       /* Any remaining right-edge blocks are only copied. */
       for (; 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 < DCTSIZE2; i++)
           *dst_ptr++ = *src_ptr++;
       }
     }
       }
     }
   }
 }
 
 
 LOCAL(void)
 do_transverse (j_decompress_ptr srcinfo, j_compress_ptr dstinfo,
            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;
   int ci, i, j, offset_x, offset_y;
   JBLOCKARRAY src_buffer, dst_buffer;
   JCOEFPTR src_ptr, dst_ptr;
   jpeg_component_info *compptr;
 
   MCU_cols = dstinfo->image_width / (dstinfo->max_h_samp_factor * DCTSIZE);
   MCU_rows = dstinfo->image_height / (dstinfo->max_v_samp_factor * DCTSIZE);
 
   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;
     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,
          (JDIMENSION) compptr->h_samp_factor, FALSE);
       for (offset_x = 0; offset_x < compptr->h_samp_factor; offset_x++) {
         if (dst_blk_y < comp_height) {
           src_ptr = src_buffer[offset_x]
         [comp_height - dst_blk_y - offset_y - 1];
           if (dst_blk_x < comp_width) {
         /* Block is within the mirrorable area. */
         dst_ptr = dst_buffer[offset_y]
           [comp_width - dst_blk_x - offset_x - 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 */
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         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 {
           src_ptr = src_buffer[offset_x][dst_blk_y + offset_y];
           if (dst_blk_x < comp_width) {
         /* Bottom-edge blocks are mirrored in x only */
         dst_ptr = dst_buffer[offset_y]
           [comp_width - dst_blk_x - offset_x - 1];
         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 */
         dst_ptr = dst_buffer[offset_y][dst_blk_x + offset_x];
         for (i = 0; i < DCTSIZE; i++)
           for (j = 0; j < DCTSIZE; j++)
             dst_ptr[j*DCTSIZE+i] = src_ptr[i*DCTSIZE+j];
           }
         }
       }
     }
       }
     }
   }
 }
 
 
 /* Request any required workspace.
  *
  * 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).
  */
 
 GLOBAL(void)
 jtransform_request_workspace (j_decompress_ptr srcinfo,
                   jpeg_transform_info *info)
 {
   jvirt_barray_ptr *coef_arrays = NULL;
   jpeg_component_info *compptr;
   int ci;
 
   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;
   }
 
   switch (info->transform) {
   case JXFORM_NONE:
   case JXFORM_FLIP_H:
     /* Don't need a workspace array */
     break;
   case JXFORM_FLIP_V:
   case JXFORM_ROT_180:
     /* Need workspace arrays having same dimensions as source image.
      * Note that we allocate arrays padded out to the next iMCU boundary,
      * so that transform routines need not worry about missing edge blocks.
      */
     coef_arrays = (jvirt_barray_ptr *)
       (*srcinfo->mem->alloc_small) ((j_common_ptr) srcinfo, JPOOL_IMAGE,
     SIZEOF(jvirt_barray_ptr) * info->num_components);
     for (ci = 0; ci < info->num_components; ci++) {
       compptr = srcinfo->comp_info + ci;
       coef_arrays[ci] = (*srcinfo->mem->request_virt_barray)
     ((j_common_ptr) srcinfo, JPOOL_IMAGE, FALSE,
      (JDIMENSION) jround_up((long) compptr->width_in_blocks,
                 (long) compptr->h_samp_factor),
      (JDIMENSION) jround_up((long) compptr->height_in_blocks,
                 (long) compptr->v_samp_factor),
      (JDIMENSION) compptr->v_samp_factor);
     }
     break;
   case JXFORM_TRANSPOSE:
   case JXFORM_TRANSVERSE:
   case JXFORM_ROT_90:
   case JXFORM_ROT_270:
     /* Need workspace arrays having transposed dimensions.
      * Note that we allocate arrays padded out to the next iMCU boundary,
      * so that transform routines need not worry about missing edge blocks.
      */
     coef_arrays = (jvirt_barray_ptr *)
       (*srcinfo->mem->alloc_small) ((j_common_ptr) srcinfo, JPOOL_IMAGE,
     SIZEOF(jvirt_barray_ptr) * info->num_components);
     for (ci = 0; ci < info->num_components; ci++) {
       compptr = srcinfo->comp_info + ci;
       coef_arrays[ci] = (*srcinfo->mem->request_virt_barray)
     ((j_common_ptr) srcinfo, JPOOL_IMAGE, FALSE,
      (JDIMENSION) jround_up((long) compptr->height_in_blocks,
                 (long) compptr->v_samp_factor),
      (JDIMENSION) jround_up((long) compptr->width_in_blocks,
                 (long) compptr->h_samp_factor),
      (JDIMENSION) compptr->h_samp_factor);
     }
     break;
   }
   info->workspace_coef_arrays = coef_arrays;
 }
 
 
 /* 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 dtemp;
   UINT16 qtemp;
 
   /* Transpose basic image dimensions */
   dtemp = dstinfo->image_width;
   dstinfo->image_width = dstinfo->image_height;
   dstinfo->image_height = dtemp;
 
   /* 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;
     }
       }
     }
   }
 }
 
 
 /* Trim off any partial iMCUs on the indicated destination edge */
 
 LOCAL(void)
 trim_right_edge (j_compress_ptr dstinfo)
 {
   int ci, max_h_samp_factor;
   JDIMENSION MCU_cols;
 
   /* We have to compute max_h_samp_factor ourselves,
    * because it hasn't been set yet in the destination
    * (and we don't want to use the source's value).
    */
   max_h_samp_factor = 1;
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     int h_samp_factor = dstinfo->comp_info[ci].h_samp_factor;
     max_h_samp_factor = MAX(max_h_samp_factor, h_samp_factor);
   }
   MCU_cols = dstinfo->image_width / (max_h_samp_factor * DCTSIZE);
   if (MCU_cols > 0)     /* can't trim to 0 pixels */
     dstinfo->image_width = MCU_cols * (max_h_samp_factor * DCTSIZE);
 }
 
 LOCAL(void)
 trim_bottom_edge (j_compress_ptr dstinfo)
 {
   int ci, max_v_samp_factor;
   JDIMENSION MCU_rows;
 
   /* We have to compute max_v_samp_factor ourselves,
    * because it hasn't been set yet in the destination
    * (and we don't want to use the source's value).
    */
   max_v_samp_factor = 1;
   for (ci = 0; ci < dstinfo->num_components; ci++) {
     int v_samp_factor = dstinfo->comp_info[ci].v_samp_factor;
     max_v_samp_factor = MAX(max_v_samp_factor, v_samp_factor);
   }
   MCU_rows = dstinfo->image_height / (max_v_samp_factor * DCTSIZE);
   if (MCU_rows > 0)     /* can't trim to 0 pixels */
     dstinfo->image_height = MCU_rows * (max_v_samp_factor * DCTSIZE);
 }
 
 
 /* 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) {
     /* We use jpeg_set_colorspace to make sure subsidiary settings get fixed
      * properly.  Among other things, the target h_samp_factor & v_samp_factor
      * will get set to 1, which typically won't match the source.
      * In fact we do this even if the source is already grayscale; that
      * provides an easy way of coercing a grayscale JPEG with funny sampling
      * factors to the customary 1,1.  (Some decoders fail on other factors.)
      */
     if ((dstinfo->jpeg_color_space == JCS_YCbCr &&
      dstinfo->num_components == 3) ||
     (dstinfo->jpeg_color_space == JCS_GRAYSCALE &&
      dstinfo->num_components == 1)) {
       /* We have to preserve the source's quantization table number. */
       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);
     }
   }
 
   /* Correct the destination's image dimensions etc if necessary */
   switch (info->transform) {
   case JXFORM_NONE:
     /* Nothing to do */
     break;
   case JXFORM_FLIP_H:
     if (info->trim)
       trim_right_edge(dstinfo);
     break;
   case JXFORM_FLIP_V:
     if (info->trim)
       trim_bottom_edge(dstinfo);
     break;
   case JXFORM_TRANSPOSE:
     transpose_critical_parameters(dstinfo);
     /* transpose does NOT have to trim anything */
     break;
   case JXFORM_TRANSVERSE:
     transpose_critical_parameters(dstinfo);
     if (info->trim) {
       trim_right_edge(dstinfo);
       trim_bottom_edge(dstinfo);
     }
     break;
   case JXFORM_ROT_90:
     transpose_critical_parameters(dstinfo);
     if (info->trim)
       trim_right_edge(dstinfo);
     break;
   case JXFORM_ROT_180:
     if (info->trim) {
       trim_right_edge(dstinfo);
       trim_bottom_edge(dstinfo);
     }
     break;
   case JXFORM_ROT_270:
     transpose_critical_parameters(dstinfo);
     if (info->trim)
       trim_bottom_edge(dstinfo);
     break;
   }
 
   /* 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_transformation (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;
 
   switch (info->transform) {
   case JXFORM_NONE:
     break;
   case JXFORM_FLIP_H:
     do_flip_h(srcinfo, dstinfo, src_coef_arrays);
     break;
   case JXFORM_FLIP_V:
     do_flip_v(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_TRANSPOSE:
     do_transpose(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_TRANSVERSE:
     do_transverse(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_ROT_90:
     do_rot_90(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_ROT_180:
     do_rot_180(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
     break;
   case JXFORM_ROT_270:
     do_rot_270(srcinfo, dstinfo, src_coef_arrays, dst_coef_arrays);
     break;
   }
 }
 
 #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
   }
 }