-struct png_tmp_buffer
-{
- char *buffer;
- size_t size;
-};
-
-static void
-pngWriteCallback(png_structp png_ptr, png_bytep data, png_size_t length)
-{
- struct png_tmp_buffer *buf = (struct png_tmp_buffer*) png_get_io_ptr(png_ptr);
- size_t nsize = buf->size + length;
-
- /* allocate or grow buffer */
- if (buf->buffer)
- buf->buffer = (char*)realloc(buf->buffer, nsize);
- else
- buf->buffer = (char*)malloc(nsize);
-
- if (!buf->buffer)
- png_error(png_ptr, "Buffer allocation error");
-
- memcpy(buf->buffer + buf->size, data, length);
- buf->size += length;
-}
-
-bool writePixelsToBuffer(unsigned char *pixels,
- unsigned width, unsigned height, unsigned numChannels,
- bool flipped,
- char **buffer,
- int *size)
-{
- struct png_tmp_buffer png_mem;
- png_structp png_ptr;
- png_infop info_ptr;
- int type;
-
- png_mem.buffer = NULL;
- png_mem.size = 0;
-
- switch (numChannels) {
- case 4:
- type = PNG_COLOR_TYPE_RGB_ALPHA;
- break;
- case 3:
- type = PNG_COLOR_TYPE_RGB;
- break;
- case 2:
- type = PNG_COLOR_TYPE_GRAY_ALPHA;
- break;
- case 1:
- type = PNG_COLOR_TYPE_GRAY;
- break;
- default:
- goto no_png;
- }
-
- png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
- if (!png_ptr)
- goto no_png;
-
- info_ptr = png_create_info_struct(png_ptr);
- if (!info_ptr) {
- png_destroy_write_struct(&png_ptr, NULL);
- goto no_png;
- }
-
- if (setjmp(png_jmpbuf(png_ptr))) {
- png_destroy_write_struct(&png_ptr, &info_ptr);
- goto no_png;
- }
-
- png_set_write_fn(png_ptr, &png_mem, pngWriteCallback, NULL);
-
- png_set_IHDR(png_ptr, info_ptr, width, height, 8,
- type, PNG_INTERLACE_NONE,
- PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
-
- png_set_compression_level(png_ptr, Z_DEFAULT_COMPRESSION);
-
- png_write_info(png_ptr, info_ptr);
-
- if (!flipped) {
- for (unsigned y = 0; y < height; ++y) {
- png_bytep row = (png_bytep)(pixels + y*width*numChannels);
- png_write_rows(png_ptr, &row, 1);
- }
- } else {
- unsigned y = height;
- while (y--) {
- png_bytep row = (png_bytep)(pixels + y*width*numChannels);
- png_write_rows(png_ptr, &row, 1);
- }
- }
-
- png_write_end(png_ptr, info_ptr);
- png_destroy_write_struct(&png_ptr, &info_ptr);
-
- *buffer = png_mem.buffer;
- *size = png_mem.size;
-
- return true;
-
-no_png:
- *buffer = NULL;
- *size = 0;
-
- if (png_mem.buffer)
- free(png_mem.buffer);
- return false;
-}