Delete SkImageDecoder

src/images/SkImageDecoder_libpng.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkColor.h"
 #include "SkColorPriv.h"
 #include "SkDither.h"
 #include "SkMath.h"
 #include "SkRTConf.h"
-#include "SkScaledBitmapSampler.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
 #include "SkUtils.h"
 #include "transform_scanline.h"
 
 #include "png.h"
 
 /* These were dropped in libpng >= 1.4 */
 #ifndef png_infopp_NULL
 #define png_infopp_NULL nullptr
@@ skipping 11 matching lines @@
 #define png_flush_ptr_NULL nullptr
 #endif
 
 #define DEFAULT_FOR_SUPPRESS_PNG_IMAGE_DECODER_WARNINGS true
 SK_CONF_DECLARE(bool, c_suppressPNGImageDecoderWarnings,
                 "images.png.suppressDecoderWarnings",
                 DEFAULT_FOR_SUPPRESS_PNG_IMAGE_DECODER_WARNINGS,
                 "Suppress most PNG warnings when calling image decode "
                 "functions.");
 
-class SkPNGImageIndex {
-public:
-    // Takes ownership of stream.
-    SkPNGImageIndex(SkStreamRewindable* stream, png_structp png_ptr, png_infop info_ptr)
-        : fStream(stream)
-        , fPng_ptr(png_ptr)
-        , fInfo_ptr(info_ptr)
-        , fColorType(kUnknown_SkColorType) {
-        SkASSERT(stream != nullptr);
-    }
-    ~SkPNGImageIndex() {
-        if (fPng_ptr) {
-            png_destroy_read_struct(&fPng_ptr, &fInfo_ptr, png_infopp_NULL);
-        }
-    }
+///////////////////////////////////////////////////////////////////////////////
 
-    SkAutoTDelete<SkStreamRewindable>   fStream;
-    png_structp                         fPng_ptr;
-    png_infop                           fInfo_ptr;
-    SkColorType                         fColorType;
-};
-
-class SkPNGImageDecoder : public SkImageDecoder {
-public:
-    SkPNGImageDecoder() {
-        fImageIndex = nullptr;
-    }
-    Format getFormat() const override {
-        return kPNG_Format;
-    }
-
-    virtual ~SkPNGImageDecoder() { delete fImageIndex; }
-
-protected:
-    Result onDecode(SkStream* stream, SkBitmap* bm, Mode) override;
-
-private:
-    SkPNGImageIndex* fImageIndex;
-
-    bool onDecodeInit(SkStream* stream, png_structp *png_ptrp, png_infop *info_ptrp);
-    bool decodePalette(png_structp png_ptr, png_infop info_ptr, int bitDepth,
-                       bool * SK_RESTRICT hasAlphap, bool *reallyHasAlphap,
-                       SkColorTable **colorTablep);
-    bool getBitmapColorType(png_structp, png_infop, SkColorType*, bool* hasAlpha,
-                            SkPMColor* theTranspColor);
-
-    typedef SkImageDecoder INHERITED;
-};
-
-#ifndef png_jmpbuf
-#  define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
-#endif
-
-#define PNG_BYTES_TO_CHECK 4
-
-/* Automatically clean up after throwing an exception */
-struct PNGAutoClean {
-    PNGAutoClean(png_structp p, png_infop i): png_ptr(p), info_ptr(i) {}
-    ~PNGAutoClean() {
-        png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
-    }
-private:
-    png_structp png_ptr;
-    png_infop info_ptr;
-};
-
-static void sk_read_fn(png_structp png_ptr, png_bytep data, png_size_t length) {
-    SkStream* sk_stream = (SkStream*) png_get_io_ptr(png_ptr);
-    size_t bytes = sk_stream->read(data, length);
-    if (bytes != length) {
-        png_error(png_ptr, "Read Error!");
-    }
-}
-
-#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
-static int sk_read_user_chunk(png_structp png_ptr, png_unknown_chunkp chunk) {
-    SkPngChunkReader* peeker = (SkPngChunkReader*)png_get_user_chunk_ptr(png_ptr);
-    // readChunk() returning true means continue decoding
-    return peeker->readChunk((const char*)chunk->name, chunk->data, chunk->size) ?
-            1 : -1;
-}
-#endif
+#include "SkColorPriv.h"
+#include "SkUnPreMultiply.h"
 
 static void sk_error_fn(png_structp png_ptr, png_const_charp msg) {
     if (!c_suppressPNGImageDecoderWarnings) {
         SkDEBUGF(("------ png error %s\n", msg));
     }
     longjmp(png_jmpbuf(png_ptr), 1);
 }
 
-static void skip_src_rows(png_structp png_ptr, uint8_t storage[], int count) {
-    for (int i = 0; i < count; i++) {
-        uint8_t* tmp = storage;
-        png_read_rows(png_ptr, &tmp, png_bytepp_NULL, 1);
-    }
-}
-
-static bool pos_le(int value, int max) {
-    return value > 0 && value <= max;
-}
-
-static bool substituteTranspColor(SkBitmap* bm, SkPMColor match) {
-    SkASSERT(bm->colorType() == kN32_SkColorType);
-
-    bool reallyHasAlpha = false;
-
-    for (int y = bm->height() - 1; y >= 0; --y) {
-        SkPMColor* p = bm->getAddr32(0, y);
-        for (int x = bm->width() - 1; x >= 0; --x) {
-            if (match == *p) {
-                *p = 0;
-                reallyHasAlpha = true;
-            }
-            p += 1;
-        }
-    }
-    return reallyHasAlpha;
-}
-
-static bool canUpscalePaletteToConfig(SkColorType dstColorType, bool srcHasAlpha) {
-    switch (dstColorType) {
-        case kN32_SkColorType:
-        case kARGB_4444_SkColorType:
-            return true;
-        case kRGB_565_SkColorType:
-            // only return true if the src is opaque (since 565 is opaque)
-            return !srcHasAlpha;
-        default:
-            return false;
-    }
-}
-
-// call only if color_type is PALETTE. Returns true if the ctable has alpha
-static bool hasTransparencyInPalette(png_structp png_ptr, png_infop info_ptr) {
-    png_bytep trans;
-    int num_trans;
-
-    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
-        png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, nullptr);
-        return num_trans > 0;
-    }
-    return false;
-}
-
-void do_nothing_warning_fn(png_structp, png_const_charp) {
-    /* do nothing */
-}
-
-bool SkPNGImageDecoder::onDecodeInit(SkStream* sk_stream, png_structp *png_ptrp,
-                                     png_infop *info_ptrp) {
-    /* 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 nullptr 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_error_ptr user_warning_fn =
-        (c_suppressPNGImageDecoderWarnings) ? (&do_nothing_warning_fn) : nullptr;
-    /* nullptr means to leave as default library behavior. */
-    /* c_suppressPNGImageDecoderWarnings default depends on SK_DEBUG. */
-    /* To suppress warnings with a SK_DEBUG binary, set the
-     * environment variable "skia_images_png_suppressDecoderWarnings"
-     * to "true".  Inside a program that links to skia:
-     * SK_CONF_SET("images.png.suppressDecoderWarnings", true); */
-
-    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
-        nullptr, sk_error_fn, user_warning_fn);
-    //   png_voidp user_error_ptr, user_error_fn, user_warning_fn);
-    if (png_ptr == nullptr) {
-        return false;
-    }
-
-    *png_ptrp = png_ptr;
-
-    /* Allocate/initialize the memory for image information. */
-    png_infop info_ptr = png_create_info_struct(png_ptr);
-    if (info_ptr == nullptr) {
-        png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
-        return false;
-    }
-    *info_ptrp = 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))) {
-        png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
-        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 */ );
-
-#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
-    // 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);
-    }
-#endif
-    /* 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 bitDepth, colorType;
-    png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bitDepth,
-                 &colorType, int_p_NULL, int_p_NULL, int_p_NULL);
-
-    /* tell libpng to strip 16 bit/color files down to 8 bits/color */
-    if (bitDepth == 16) {
-        png_set_strip_16(png_ptr);
-    }
-#ifdef PNG_READ_PACK_SUPPORTED
-    /* 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 (bitDepth < 8) {
-        png_set_packing(png_ptr);
-    }
-#endif
-    /* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
-    if (colorType == PNG_COLOR_TYPE_GRAY && bitDepth < 8) {
-        png_set_expand_gray_1_2_4_to_8(png_ptr);
-    }
-
-    return true;
-}
-
-SkImageDecoder::Result SkPNGImageDecoder::onDecode(SkStream* sk_stream, SkBitmap* decodedBitmap,
-                                                   Mode mode) {
-    png_structp png_ptr;
-    png_infop info_ptr;
-
-    if (!onDecodeInit(sk_stream, &png_ptr, &info_ptr)) {
-        return kFailure;
-    }
-
-    PNGAutoClean autoClean(png_ptr, info_ptr);
-
-    if (setjmp(png_jmpbuf(png_ptr))) {
-        return kFailure;
-    }
-
-    png_uint_32 origWidth, origHeight;
-    int bitDepth, pngColorType, interlaceType;
-    png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bitDepth,
-                 &pngColorType, &interlaceType, int_p_NULL, int_p_NULL);
-
-    SkColorType         colorType;
-    bool                hasAlpha = false;
-    SkPMColor           theTranspColor = 0; // 0 tells us not to try to match
-
-    if (!this->getBitmapColorType(png_ptr, info_ptr, &colorType, &hasAlpha, &theTranspColor)) {
-        return kFailure;
-    }
-
-    SkAlphaType alphaType = this->getRequireUnpremultipliedColors() ?
-                                kUnpremul_SkAlphaType : kPremul_SkAlphaType;
-    const int sampleSize = this->getSampleSize();
-    SkScaledBitmapSampler sampler(origWidth, origHeight, sampleSize);
-    decodedBitmap->setInfo(SkImageInfo::Make(sampler.scaledWidth(), sampler.scaledHeight(),
-                                             colorType, alphaType));
-
-    if (SkImageDecoder::kDecodeBounds_Mode == mode) {
-        return kSuccess;
-    }
-
-    // from here down we are concerned with colortables and pixels
-
-    // we track if we actually see a non-opaque pixels, since sometimes a PNG sets its colortype
-    // to |= PNG_COLOR_MASK_ALPHA, but all of its pixels are in fact opaque. We care, since we
-    // draw lots faster if we can flag the bitmap has being opaque
-    bool reallyHasAlpha = false;
-    SkColorTable* colorTable = nullptr;
-
-    if (pngColorType == PNG_COLOR_TYPE_PALETTE) {
-        decodePalette(png_ptr, info_ptr, bitDepth, &hasAlpha, &reallyHasAlpha, &colorTable);
-    }
-
-    SkAutoUnref aur(colorTable);
-
-    if (!this->allocPixelRef(decodedBitmap,
-                             kIndex_8_SkColorType == colorType ? colorTable : nullptr)) {
-        return kFailure;
-    }
-
-    SkAutoLockPixels alp(*decodedBitmap);
-
-    // Repeat setjmp, otherwise variables declared since the last call (e.g. alp
-    // and aur) won't get their destructors called in case of a failure.
-    if (setjmp(png_jmpbuf(png_ptr))) {
-        return kFailure;
-    }
-
-    /* Turn on interlace handling.  REQUIRED if you are not using
-    *  png_read_image().  To see how to handle interlacing passes,
-    *  see the png_read_row() method below:
-    */
-    const int number_passes = (interlaceType != PNG_INTERLACE_NONE) ?
-                              png_set_interlace_handling(png_ptr) : 1;
-
-    /* Optional call to gamma correct and add the background to the palette
-    *  and update info structure.  REQUIRED if you are expecting libpng to
-    *  update the palette for you (ie you selected such a transform above).
-    */
-    png_read_update_info(png_ptr, info_ptr);
-
-    if ((kAlpha_8_SkColorType == colorType || kIndex_8_SkColorType == colorType) &&
-            1 == sampleSize) {
-        if (kAlpha_8_SkColorType == colorType) {
-            // For an A8 bitmap, we assume there is an alpha for speed. It is
-            // possible the bitmap is opaque, but that is an unlikely use case
-            // since it would not be very interesting.
-            reallyHasAlpha = true;
-            // A8 is only allowed if the original was GRAY.
-            SkASSERT(PNG_COLOR_TYPE_GRAY == pngColorType);
-        }
-        for (int i = 0; i < number_passes; i++) {
-            for (png_uint_32 y = 0; y < origHeight; y++) {
-                uint8_t* bmRow = decodedBitmap->getAddr8(0, y);
-                png_read_rows(png_ptr, &bmRow, png_bytepp_NULL, 1);
-            }
-        }
-    } else {
-        SkScaledBitmapSampler::SrcConfig sc;
-        int srcBytesPerPixel = 4;
-
-        if (colorTable != nullptr) {
-            sc = SkScaledBitmapSampler::kIndex;
-            srcBytesPerPixel = 1;
-        } else if (kAlpha_8_SkColorType == colorType) {
-            // A8 is only allowed if the original was GRAY.
-            SkASSERT(PNG_COLOR_TYPE_GRAY == pngColorType);
-            sc = SkScaledBitmapSampler::kGray;
-            srcBytesPerPixel = 1;
-        } else if (hasAlpha) {
-            sc = SkScaledBitmapSampler::kRGBA;
-        } else {
-            sc = SkScaledBitmapSampler::kRGBX;
-        }
-
-        /*  We have to pass the colortable explicitly, since we may have one
-            even if our decodedBitmap doesn't, due to the request that we
-            upscale png's palette to a direct model
-         */
-        const SkPMColor* colors = colorTable ? colorTable->readColors() : nullptr;
-        if (!sampler.begin(decodedBitmap, sc, *this, colors)) {
-            return kFailure;
-        }
-        const int height = decodedBitmap->height();
-
-        if (number_passes > 1) {
-            SkAutoTMalloc<uint8_t> storage(origWidth * origHeight * srcBytesPerPixel);
-            uint8_t* base = storage.get();
-            size_t rowBytes = origWidth * srcBytesPerPixel;
-
-            for (int i = 0; i < number_passes; i++) {
-                uint8_t* row = base;
-                for (png_uint_32 y = 0; y < origHeight; y++) {
-                    uint8_t* bmRow = row;
-                    png_read_rows(png_ptr, &bmRow, png_bytepp_NULL, 1);
-                    row += rowBytes;
-                }
-            }
-            // now sample it
-            base += sampler.srcY0() * rowBytes;
-            for (int y = 0; y < height; y++) {
-                reallyHasAlpha |= sampler.next(base);
-                base += sampler.srcDY() * rowBytes;
-            }
-        } else {
-            SkAutoTMalloc<uint8_t> storage(origWidth * srcBytesPerPixel);
-            uint8_t* srcRow = storage.get();
-            skip_src_rows(png_ptr, srcRow, sampler.srcY0());
-
-            for (int y = 0; y < height; y++) {
-                uint8_t* tmp = srcRow;
-                png_read_rows(png_ptr, &tmp, png_bytepp_NULL, 1);
-                reallyHasAlpha |= sampler.next(srcRow);
-                if (y < height - 1) {
-                    skip_src_rows(png_ptr, srcRow, sampler.srcDY() - 1);
-                }
-            }
-
-            // skip the rest of the rows (if any)
-            png_uint_32 read = (height - 1) * sampler.srcDY() +
-                               sampler.srcY0() + 1;
-            SkASSERT(read <= origHeight);
-            skip_src_rows(png_ptr, srcRow, origHeight - read);
-        }
-    }
-
-    /* read rest of file, and get additional chunks in info_ptr - REQUIRED */
-    png_read_end(png_ptr, info_ptr);
-
-    if (0 != theTranspColor) {
-        reallyHasAlpha |= substituteTranspColor(decodedBitmap, theTranspColor);
-    }
-    if (reallyHasAlpha && this->getRequireUnpremultipliedColors()) {
-        switch (decodedBitmap->colorType()) {
-            case kIndex_8_SkColorType:
-                // Fall through.
-            case kARGB_4444_SkColorType:
-                // We have chosen not to support unpremul for these colortypes.
-                return kFailure;
-            default: {
-                // Fall through to finish the decode. This colortype either
-                // supports unpremul or it is irrelevant because it has no
-                // alpha (or only alpha).
-                // These brackets prevent a warning.
-            }
-        }
-    }
-
-    if (!reallyHasAlpha) {
-        decodedBitmap->setAlphaType(kOpaque_SkAlphaType);
-    }
-    return kSuccess;
-}
-
-
-
-bool SkPNGImageDecoder::getBitmapColorType(png_structp png_ptr, png_infop info_ptr,
-                                           SkColorType* colorTypep,
-                                           bool* hasAlphap,
-                                           SkPMColor* SK_RESTRICT theTranspColorp) {
-    png_uint_32 origWidth, origHeight;
-    int bitDepth, colorType;
-    png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bitDepth,
-                 &colorType, int_p_NULL, int_p_NULL, int_p_NULL);
-
-#ifdef PNG_sBIT_SUPPORTED
-    // check for sBIT chunk data, in case we should disable dithering because
-    // our data is not truely 8bits per component
-    png_color_8p sig_bit;
-    if (this->getDitherImage() && png_get_sBIT(png_ptr, info_ptr, &sig_bit)) {
-#if 0
-        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 (pos_le(sig_bit->red, SK_R16_BITS) &&
-            pos_le(sig_bit->green, SK_G16_BITS) &&
-            pos_le(sig_bit->blue, SK_B16_BITS)) {
-            this->setDitherImage(false);
-        }
-    }
-#endif
-
-    if (colorType == PNG_COLOR_TYPE_PALETTE) {
-        bool paletteHasAlpha = hasTransparencyInPalette(png_ptr, info_ptr);
-        *colorTypep = this->getPrefColorType(kIndex_SrcDepth, paletteHasAlpha);
-        // now see if we can upscale to their requested colortype
-        if (!canUpscalePaletteToConfig(*colorTypep, paletteHasAlpha)) {
-            *colorTypep = kIndex_8_SkColorType;
-        }
-    } else {
-        png_color_16p transpColor = nullptr;
-        int numTransp = 0;
-
-        png_get_tRNS(png_ptr, info_ptr, nullptr, &numTransp, &transpColor);
-
-        bool valid = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS);
-
-        if (valid && numTransp == 1 && transpColor != nullptr) {
-            /*  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 (colorType & PNG_COLOR_MASK_COLOR) {
-                if (16 == bitDepth) {
-                    *theTranspColorp = SkPackARGB32(0xFF, transpColor->red >> 8,
-                                                    transpColor->green >> 8,
-                                                    transpColor->blue >> 8);
-                } else {
-                    /* We apply the mask because in a very small
-                       number of corrupt PNGs, (transpColor->red > 255)
-                       and (bitDepth == 8), for certain versions of libpng. */
-                    *theTranspColorp = SkPackARGB32(0xFF,
-                                                    0xFF & (transpColor->red),
-                                                    0xFF & (transpColor->green),
-                                                    0xFF & (transpColor->blue));
-                }
-            } else {    // gray
-                if (16 == bitDepth) {
-                    *theTranspColorp = SkPackARGB32(0xFF, transpColor->gray >> 8,
-                                                    transpColor->gray >> 8,
-                                                    transpColor->gray >> 8);
-                } else {
-                    /* We apply the mask because in a very small
-                       number of corrupt PNGs, (transpColor->red >
-                       255) and (bitDepth == 8), for certain versions
-                       of libpng.  For safety we assume the same could
-                       happen with a grayscale PNG.  */
-                    *theTranspColorp = SkPackARGB32(0xFF,
-                                                    0xFF & (transpColor->gray),
-                                                    0xFF & (transpColor->gray),
-                                                    0xFF & (transpColor->gray));
-                }
-            }
-        }
-
-        if (valid ||
-            PNG_COLOR_TYPE_RGB_ALPHA == colorType ||
-            PNG_COLOR_TYPE_GRAY_ALPHA == colorType) {
-            *hasAlphap = true;
-        }
-
-        SrcDepth srcDepth = k32Bit_SrcDepth;
-        if (PNG_COLOR_TYPE_GRAY == colorType) {
-            srcDepth = k8BitGray_SrcDepth;
-            // Remove this assert, which fails on desk_pokemonwiki.skp
-            //SkASSERT(!*hasAlphap);
-        }
-
-        *colorTypep = this->getPrefColorType(srcDepth, *hasAlphap);
-        // now match the request against our capabilities
-        if (*hasAlphap) {
-            if (*colorTypep != kARGB_4444_SkColorType) {
-                *colorTypep = kN32_SkColorType;
-            }
-        } else {
-            if (kAlpha_8_SkColorType == *colorTypep) {
-                if (k8BitGray_SrcDepth != srcDepth) {
-                    // Converting a non grayscale image to A8 is not currently supported.
-                    *colorTypep = kN32_SkColorType;
-                }
-            } else if (*colorTypep != kRGB_565_SkColorType &&
-                       *colorTypep != kARGB_4444_SkColorType) {
-                *colorTypep = kN32_SkColorType;
-            }
-        }
-    }
-
-    // sanity check for size
-    {
-        int64_t size = sk_64_mul(origWidth, origHeight);
-        // now check that if we are 4-bytes per pixel, we also don't overflow
-        if (size < 0 || size > (0x7FFFFFFF >> 2)) {
-            return false;
-        }
-    }
-
-    // If the image has alpha and the decoder wants unpremultiplied
-    // colors, the only supported colortype is 8888.
-    if (this->getRequireUnpremultipliedColors() && *hasAlphap) {
-        *colorTypep = kN32_SkColorType;
-    }
-
-    if (fImageIndex != nullptr) {
-        if (kUnknown_SkColorType == fImageIndex->fColorType) {
-            // This is the first time for this subset decode. From now on,
-            // all decodes must be in the same colortype.
-            fImageIndex->fColorType = *colorTypep;
-        } else if (fImageIndex->fColorType != *colorTypep) {
-            // Requesting a different colortype for a subsequent decode is not
-            // supported. Report failure before we make changes to png_ptr.
-            return false;
-        }
-    }
-
-    bool convertGrayToRGB = PNG_COLOR_TYPE_GRAY == colorType && *colorTypep != kAlpha_8_SkColorType;
-
-    // Unless the user is requesting A8, convert a grayscale image into RGB.
-    // GRAY_ALPHA will always be converted to RGB
-    if (convertGrayToRGB || colorType == PNG_COLOR_TYPE_GRAY_ALPHA) {
-        png_set_gray_to_rgb(png_ptr);
-    }
-
-    // Add filler (or alpha) byte (after each RGB triplet) if necessary.
-    if (colorType == PNG_COLOR_TYPE_RGB || convertGrayToRGB) {
-        png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER);
-    }
-
-    return true;
-}
-
-typedef uint32_t (*PackColorProc)(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
-
-bool SkPNGImageDecoder::decodePalette(png_structp png_ptr, png_infop info_ptr,
-                                      int bitDepth, bool *hasAlphap,
-                                      bool *reallyHasAlphap,
-                                      SkColorTable **colorTablep) {
-    int numPalette;
-    png_colorp palette;
-    png_bytep trans;
-    int numTrans;
-
-    png_get_PLTE(png_ptr, info_ptr, &palette, &numPalette);
-
-    SkPMColor colorStorage[256];    // worst-case storage
-    SkPMColor* colorPtr = colorStorage;
-
-    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
-        png_get_tRNS(png_ptr, info_ptr, &trans, &numTrans, nullptr);
-        *hasAlphap = (numTrans > 0);
-    } else {
-        numTrans = 0;
-    }
-
-    // check for bad images that might make us crash
-    if (numTrans > numPalette) {
-        numTrans = numPalette;
-    }
-
-    int index = 0;
-    int transLessThanFF = 0;
-
-    // Choose which function to use to create the color table. If the final destination's
-    // colortype is unpremultiplied, the color table will store unpremultiplied colors.
-    PackColorProc proc;
-    if (this->getRequireUnpremultipliedColors()) {
-        proc = &SkPackARGB32NoCheck;
-    } else {
-        proc = &SkPreMultiplyARGB;
-    }
-    for (; index < numTrans; index++) {
-        transLessThanFF |= (int)*trans - 0xFF;
-        *colorPtr++ = proc(*trans++, palette->red, palette->green, palette->blue);
-        palette++;
-    }
-    bool reallyHasAlpha = (transLessThanFF < 0);
-
-    for (; index < numPalette; index++) {
-        *colorPtr++ = SkPackARGB32(0xFF, palette->red, palette->green, palette->blue);
-        palette++;
-    }
-
-    /*  BUGGY IMAGE WORKAROUND
-
-        Invalid images could contain pixel values that are greater than the number of palette
-        entries. Since we use pixel values as indices into the palette this could result in reading
-        beyond the end of the palette which could leak the contents of uninitialized memory. To
-        ensure this doesn't happen, we grow the colortable to the maximum size that can be
-        addressed by the bitdepth of the image and fill it with the last palette color or black if
-        the palette is empty (really broken image).
-    */
-    int colorCount = SkTMax(numPalette, 1 << SkTMin(bitDepth, 8));
-    SkPMColor lastColor = index > 0 ? colorPtr[-1] : SkPackARGB32(0xFF, 0, 0, 0);
-    for (; index < colorCount; index++) {
-        *colorPtr++ = lastColor;
-    }
-
-    *colorTablep = new SkColorTable(colorStorage, colorCount);
-    *reallyHasAlphap = reallyHasAlpha;
-    return true;
-}
-
-///////////////////////////////////////////////////////////////////////////////
-
-#include "SkColorPriv.h"
-#include "SkUnPreMultiply.h"
-
 static void sk_write_fn(png_structp png_ptr, png_bytep data, png_size_t len) {
     SkWStream* sk_stream = (SkWStream*)png_get_io_ptr(png_ptr);
     if (!sk_stream->write(data, len)) {
         png_error(png_ptr, "sk_write_fn Error!");
     }
 }
 
 static transform_scanline_proc choose_proc(SkColorType ct, bool hasAlpha) {
     // we don't care about search on alpha if we're kIndex8, since only the
     // colortable packing cares about that distinction, not the pixels
@@ skipping 260 matching lines @@
     }
 
     png_write_end(png_ptr, info_ptr);
 
     /* clean up after the write, and free any memory allocated */
     png_destroy_write_struct(&png_ptr, &info_ptr);
     return true;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
-DEFINE_DECODER_CREATOR(PNGImageDecoder);
 DEFINE_ENCODER_CREATOR(PNGImageEncoder);
 ///////////////////////////////////////////////////////////////////////////////
 
-static bool is_png(SkStreamRewindable* stream) {
-    char buf[PNG_BYTES_TO_CHECK];
-    if (stream->read(buf, PNG_BYTES_TO_CHECK) == PNG_BYTES_TO_CHECK &&
-        !png_sig_cmp((png_bytep) buf, (png_size_t)0, PNG_BYTES_TO_CHECK)) {
-        return true;
-    }
-    return false;
-}
-
-SkImageDecoder* sk_libpng_dfactory(SkStreamRewindable* stream) {
-    if (is_png(stream)) {
-        return new SkPNGImageDecoder;
-    }
-    return nullptr;
-}
-
-static SkImageDecoder::Format get_format_png(SkStreamRewindable* stream) {
-    if (is_png(stream)) {
-        return SkImageDecoder::kPNG_Format;
-    }
-    return SkImageDecoder::kUnknown_Format;
-}
-
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? new SkPNGImageEncoder : nullptr;
 }
 
-static SkImageDecoder_DecodeReg gDReg(sk_libpng_dfactory);
-static SkImageDecoder_FormatReg gFormatReg(get_format_png);
 static SkImageEncoder_EncodeReg gEReg(sk_libpng_efactory);