File indexing completed on 2024-10-06 10:23:48

 // SPDX-FileCopyrightText: 2018 Wolt Enterprises
 // SPDX-License-Identifier: MIT
 
 #include "blurhash.h"
 
 #include <math.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 #include <vector>
 
 namespace
 {
 const char chars[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#$%*+,-.:;=?@[]^_{|}~";
 
 struct Color {
     float r = 0;
     float g = 0;
     float b = 0;
 };
 
 inline int linearTosRGB(float value)
 {
     float v = fmaxf(0, fminf(1, value));
     if (v <= 0.0031308)
         return v * 12.92 * 255 + 0.5;
     else
         return (1.055 * powf(v, 1 / 2.4) - 0.055) * 255 + 0.5;
 }
 
 inline float sRGBToLinear(int value)
 {
     float v = (float)value / 255;
     if (v <= 0.04045)
         return v / 12.92;
     else
         return powf((v + 0.055) / 1.055, 2.4);
 }
 
 inline float signPow(float value, float exp)
 {
     return copysignf(powf(fabsf(value), exp), value);
 }
 
 inline uint8_t clampToUByte(int *src)
 {
     if (*src >= 0 && *src <= 255) {
         return *src;
     }
     return (*src < 0) ? 0 : 255;
 }
 
 inline uint8_t *createByteArray(int size)
 {
     return (uint8_t *)malloc(size * sizeof(uint8_t));
 }
 
 int decodeToInt(const char *string, int start, int end)
 {
     int value = 0;
     for (int iter1 = start; iter1 < end; iter1++) {
         int index = -1;
         for (int iter2 = 0; iter2 < 83; iter2++) {
             if (chars[iter2] == string[iter1]) {
                 index = iter2;
                 break;
             }
         }
         if (index == -1) {
             return -1;
         }
         value = value * 83 + index;
     }
     return value;
 }
 
 void decodeDC(int value, Color *color)
 {
     color->r = sRGBToLinear(value >> 16);
     color->g = sRGBToLinear((value >> 8) & 255);
     color->b = sRGBToLinear(value & 255);
 }
 
 void decodeAC(int value, float maximumValue, Color *color)
 {
     int quantR = (int)floorf(value / (19 * 19));
     int quantG = (int)floorf(value / 19) % 19;
     int quantB = (int)value % 19;
 
     color->r = signPow(((float)quantR - 9) / 9, 2.0) * maximumValue;
     color->g = signPow(((float)quantG - 9) / 9, 2.0) * maximumValue;
     color->b = signPow(((float)quantB - 9) / 9, 2.0) * maximumValue;
 }
 
 int decodeToArray(const char *blurhash, int width, int height, int punch, int nChannels, uint8_t *pixelArray)
 {
     if (!isValidBlurhash(blurhash)) {
         return -1;
     }
     if (punch < 1) {
         punch = 1;
     }
 
     int sizeFlag = decodeToInt(blurhash, 0, 1);
     int numY = (int)floorf(sizeFlag / 9) + 1;
     int numX = (sizeFlag % 9) + 1;
     int iter = 0;
 
     Color color;
     int quantizedMaxValue = decodeToInt(blurhash, 1, 2);
     if (quantizedMaxValue == -1) {
         return -1;
     }
 
     const float maxValue = ((float)(quantizedMaxValue + 1)) / 166;
 
     const int colors_size = numX * numY;
 
     std::vector<Color> colors(colors_size, {0, 0, 0});
 
     for (iter = 0; iter < colors_size; iter++) {
         if (iter == 0) {
             int value = decodeToInt(blurhash, 2, 6);
             if (value == -1) {
                 return -1;
             }
             decodeDC(value, &color);
             colors[iter] = color;
         } else {
             int value = decodeToInt(blurhash, 4 + iter * 2, 6 + iter * 2);
             if (value == -1) {
                 return -1;
             }
             decodeAC(value, maxValue * punch, &color);
             colors[iter] = color;
         }
     }
 
     int bytesPerRow = width * nChannels;
     int x = 0, y = 0, i = 0, j = 0;
     int intR = 0, intG = 0, intB = 0;
 
     for (y = 0; y < height; y++) {
         for (x = 0; x < width; x++) {
             float r = 0, g = 0, b = 0;
 
             for (j = 0; j < numY; j++) {
                 for (i = 0; i < numX; i++) {
                     float basics = cos((M_PI * x * i) / width) * cos((M_PI * y * j) / height);
                     int idx = i + j * numX;
                     r += colors[idx].r * basics;
                     g += colors[idx].g * basics;
                     b += colors[idx].b * basics;
                 }
             }
 
             intR = linearTosRGB(r);
             intG = linearTosRGB(g);
             intB = linearTosRGB(b);
 
             pixelArray[nChannels * x + 0 + y * bytesPerRow] = clampToUByte(&intR);
             pixelArray[nChannels * x + 1 + y * bytesPerRow] = clampToUByte(&intG);
             pixelArray[nChannels * x + 2 + y * bytesPerRow] = clampToUByte(&intB);
 
             if (nChannels == 4) {
                 pixelArray[nChannels * x + 3 + y * bytesPerRow] = 255;
             }
         }
     }
     return 0;
 }
 }
 
 uint8_t *decode(const char *blurhash, int width, int height, int punch, int nChannels)
 {
     int bytesPerRow = width * nChannels;
     uint8_t *pixelArray = createByteArray(bytesPerRow * height);
 
     if (decodeToArray(blurhash, width, height, punch, nChannels, pixelArray) == -1) {
         return NULL;
     }
     return pixelArray;
 }
 
 bool isValidBlurhash(const char *blurhash)
 {
     const int hashLength = strlen(blurhash);
 
     if (!blurhash || strlen(blurhash) < 6) {
         return false;
     }
 
     int sizeFlag = decodeToInt(blurhash, 0, 1);
     int numY = (int)floorf(sizeFlag / 9) + 1;
     int numX = (sizeFlag % 9) + 1;
 
     return hashLength == 4 + 2 * numX * numY;
 }