bool SkPNGImageDecoder::getBitmapConfig(png_structp png_ptr, png_infop info_ptr,
SkBitmap::Config *configp, bool *hasAlphap, bool *doDitherp,
SkPMColor *theTranspColorp) {
png_uint_32 origWidth, origHeight;
int bit_depth, color_type, interlace_type;
png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bit_depth,
&color_type, &interlace_type, int_p_NULL, int_p_NULL);
// check for sBIT chunk data, in case we should disable dithering because
// our data is not truely 8bits per component
if (*doDitherp) {
#if 0
SkDebugf("----- sBIT %d %d %d %d\n", info_ptr->sig_bit.red,
info_ptr->sig_bit.green, info_ptr->sig_bit.blue,
info_ptr->sig_bit.alpha);
#endif
// 0 seems to indicate no information available
if (pos_le(info_ptr->sig_bit.red, SK_R16_BITS) &&
pos_le(info_ptr->sig_bit.green, SK_G16_BITS) &&
pos_le(info_ptr->sig_bit.blue, SK_B16_BITS)) {
*doDitherp = false;
}
}
if (color_type == PNG_COLOR_TYPE_PALETTE) {
bool paletteHasAlpha = hasTransparencyInPalette(png_ptr, info_ptr);
*configp = this->getPrefConfig(kIndex_SrcDepth, paletteHasAlpha);
// now see if we can upscale to their requested config
if (!canUpscalePaletteToConfig(*configp, paletteHasAlpha)) {
*configp = SkBitmap::kIndex8_Config;
}
} else {
png_color_16p transpColor = NULL;
int numTransp = 0;
png_get_tRNS(png_ptr, info_ptr, NULL, &numTransp, &transpColor);
bool valid = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS);
if (valid && numTransp == 1 && transpColor != NULL) {
/* Compute our transparent color, which we'll match against later.
We don't really handle 16bit components properly here, since we
do our compare *after* the values have been knocked down to 8bit
which means we will find more matches than we should. The real
fix seems to be to see the actual 16bit components, do the
compare, and then knock it down to 8bits ourselves.
*/
if (color_type & PNG_COLOR_MASK_COLOR) {
if (16 == bit_depth) {
*theTranspColorp = SkPackARGB32(0xFF, transpColor->red >> 8,
transpColor->green >> 8, transpColor->blue >> 8);
} else {
*theTranspColorp = SkPackARGB32(0xFF, transpColor->red,
transpColor->green, transpColor->blue);
}
} else { // gray
if (16 == bit_depth) {
bool SkPNGImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* decodedBitmap,
Mode mode) {
// SkAutoTrace apr("SkPNGImageDecoder::onDecode");
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
* you can supply NULL for the last three parameters. We also supply the
* the compiler header file version, so that we know if the application
* was compiled with a compatible version of the library. */
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
NULL, sk_error_fn, NULL);
// png_voidp user_error_ptr, user_error_fn, user_warning_fn);
if (png_ptr == NULL) {
return false;
}
/* Allocate/initialize the memory for image information. */
png_infop info_ptr = png_create_info_struct(png_ptr);
if (info_ptr == NULL) {
png_destroy_read_struct(&png_ptr, NULL, NULL);
return false;
}
PNGAutoClean autoClean(png_ptr, info_ptr);
/* Set error handling if you are using the setjmp/longjmp method (this is
* the normal method of doing things with libpng). REQUIRED unless you
* set up your own error handlers in the png_create_read_struct() earlier.
*/
if (setjmp(png_jmpbuf(png_ptr))) {
return false;
}
/* If you are using replacement read functions, instead of calling
* png_init_io() here you would call:
*/
png_set_read_fn(png_ptr, (void *)sk_stream, sk_read_fn);
/* where user_io_ptr is a structure you want available to the callbacks */
/* If we have already read some of the signature */
// png_set_sig_bytes(png_ptr, 0 /* sig_read */ );
// hookup our peeker so we can see any user-chunks the caller may be interested in
png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_ALWAYS, (png_byte*)"", 0);
if (this->getPeeker()) {
png_set_read_user_chunk_fn(png_ptr, (png_voidp)this->getPeeker(), sk_read_user_chunk);
}
/* The call to png_read_info() gives us all of the information from the
* PNG file before the first IDAT (image data chunk). */
png_read_info(png_ptr, info_ptr);
png_uint_32 origWidth, origHeight;
int bit_depth, color_type, interlace_type;
png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bit_depth, &color_type,
&interlace_type, NULL, NULL);
/* tell libpng to strip 16 bit/color files down to 8 bits/color */
if (bit_depth == 16) {
png_set_strip_16(png_ptr);
}
/* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
* byte into separate bytes (useful for paletted and grayscale images). */
if (bit_depth < 8) {
png_set_packing(png_ptr);
}
/* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
png_set_expand_gray_1_2_4_to_8(png_ptr);
}
/* Make a grayscale image into RGB. */
if (color_type == PNG_COLOR_TYPE_GRAY ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
png_set_gray_to_rgb(png_ptr);
}
SkBitmap::Config config;
bool hasAlpha = false;
bool doDither = this->getDitherImage();
SkPMColor theTranspColor = 0; // 0 tells us not to try to match
// check for sBIT chunk data, in case we should disable dithering because
// our data is not truely 8bits per component
if (doDither) {
png_color_8p sig_bit = NULL;
bool has_sbit = PNG_INFO_sBIT == png_get_sBIT(png_ptr, info_ptr,
&sig_bit);
#if 0
if (has_sbit) {
SkDebugf("----- sBIT %d %d %d %d\n", sig_bit->red, sig_bit->green,
sig_bit->blue, sig_bit->alpha);
}
#endif
// 0 seems to indicate no information available
if (has_sbit && pos_le(sig_bit->red, SK_R16_BITS) &&
pos_le(sig_bit->green, SK_G16_BITS) &&
pos_le(sig_bit->blue, SK_B16_BITS)) {
doDither = false;
}
}
if (color_type == PNG_COLOR_TYPE_PALETTE) {
bool paletteHasAlpha = hasTransparencyInPalette(png_ptr, info_ptr);
config = this->getPrefConfig(kIndex_SrcDepth, paletteHasAlpha);
// now see if we can upscale to their requested config
if (!canUpscalePaletteToConfig(config, paletteHasAlpha)) {
config = SkBitmap::kIndex8_Config;
}
} else {
png_color_16p transpColor = NULL;
int numTransp = 0;
png_get_tRNS(png_ptr, info_ptr, NULL, &numTransp, &transpColor);
bool valid = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS);
if (valid && numTransp == 1 && transpColor != NULL) {
/* Compute our transparent color, which we'll match against later.
We don't really handle 16bit components properly here, since we
do our compare *after* the values have been knocked down to 8bit
which means we will find more matches than we should. The real
fix seems to be to see the actual 16bit components, do the
compare, and then knock it down to 8bits ourselves.
*/
if (color_type & PNG_COLOR_MASK_COLOR) {
if (16 == bit_depth) {
theTranspColor = SkPackARGB32(0xFF, transpColor->red >> 8,
transpColor->green >> 8, transpColor->blue >> 8);
} else {
theTranspColor = SkPackARGB32(0xFF, transpColor->red,
transpColor->green, transpColor->blue);
}
} else { // gray
if (16 == bit_depth) {
