static void copyBGRDataFromMMBitmap(MMBitmapRef bitmap, uint8_t *dest)
{
if (MMRGB_IS_BGR && (bitmap->bytewidth % 4) == 0) { /* No conversion needed. */
memcpy(dest, bitmap->imageBuffer, bitmap->bytewidth * bitmap->height);
} else { /* Convert to RGB with other-than-4-byte alignment. */
const size_t bytewidth = (bitmap->width * bitmap->bytesPerPixel + 3) & ~3;
size_t y;
/* Copy image data row by row. */
for (y = 0; y < bitmap->height; ++y) {
uint8_t *rowptr = dest + (y * bytewidth);
size_t x;
for (x = 0; x < bitmap->width; ++x) {
MMRGBColor *color = MMRGBColorRefAtPoint(bitmap, x, y);
/* BMP files are stored in BGR format. */
rowptr[0] = color->blue;
rowptr[1] = color->green;
rowptr[2] = color->red;
rowptr += bitmap->bytesPerPixel;
}
}
}
}
/* Returns pointer to PNGWriteInfo struct containing data ready to be used with
* functions such as png_write_png().
*
* It is the caller's responsibility to destroy() the returned structure with
* destroyPNGWriteInfo(). */
static PNGWriteInfoRef createPNGWriteInfo(MMBitmapRef bitmap)
{
PNGWriteInfoRef info = malloc(sizeof(PNGWriteInfo));
png_uint_32 y;
if (info == NULL) return NULL;
info->png_ptr = NULL;
info->info_ptr = NULL;
info->row_pointers = NULL;
assert(bitmap != NULL);
/* Initialize the write struct. */
info->png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
NULL, NULL, NULL);
if (info->png_ptr == NULL) goto bail;
/* Set up error handling. */
if (setjmp(png_jmpbuf(info->png_ptr))) {
png_destroy_write_struct(&(info->png_ptr), &(info->info_ptr));
goto bail;
}
/* Initialize the info struct. */
info->info_ptr = png_create_info_struct(info->png_ptr);
if (info->info_ptr == NULL) {
png_destroy_write_struct(&(info->png_ptr), NULL);
goto bail;
}
/* Set image attributes. */
png_set_IHDR(info->png_ptr,
info->info_ptr,
bitmap->width,
bitmap->height,
8,
PNG_COLOR_TYPE_RGB,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
info->row_count = bitmap->height;
info->row_pointers = png_malloc(info->png_ptr,
sizeof(png_byte *) * info->row_count);
if (bitmap->bytesPerPixel == 3) {
/* No alpha channel; image data can be copied directly. */
for (y = 0; y < info->row_count; ++y) {
info->row_pointers[y] = bitmap->imageBuffer + (bitmap->bytewidth * y);
}
info->free_row_pointers = false;
/* Convert BGR to RGB if necessary. */
if (MMRGB_IS_BGR) {
png_set_bgr(info->png_ptr);
}
} else {
/* Ignore alpha channel; copy image data row by row. */
const size_t bytesPerPixel = 3;
const size_t bytewidth = ADD_PADDING(bitmap->width * bytesPerPixel);
for (y = 0; y < info->row_count; ++y) {
png_uint_32 x;
png_byte *row_ptr = png_malloc(info->png_ptr, bytewidth);
info->row_pointers[y] = row_ptr;
for (x = 0; x < bitmap->width; ++x) {
MMRGBColor *color = MMRGBColorRefAtPoint(bitmap, x, y);
row_ptr[0] = color->red;
row_ptr[1] = color->green;
row_ptr[2] = color->blue;
row_ptr += bytesPerPixel;
}
}
info->free_row_pointers = true;
}
png_set_rows(info->png_ptr, info->info_ptr, info->row_pointers);
return info;
bail:
if (info != NULL) free(info);
return NULL;
}
