Delete dead SkImageDecoder::buildTileIndex and decodeSubset code

src/images/SkImageDecoder_libpng.cpp

Index: src/images/SkImageDecoder_libpng.cpp
diff --git a/src/images/SkImageDecoder_libpng.cpp b/src/images/SkImageDecoder_libpng.cpp
index bcf8196f4d9478f72961e69b278b4373287fcdd4..47963b5543ece7d3c8224340c8c6f34056eee7c6 100644
--- a/src/images/SkImageDecoder_libpng.cpp
+++ b/src/images/SkImageDecoder_libpng.cpp
@@ -82,10 +82,6 @@ public:
     virtual ~SkPNGImageDecoder() { delete fImageIndex; }
 
 protected:
-#ifdef SK_PNG_INDEX_SUPPORTED
-    bool onBuildTileIndex(SkStreamRewindable *stream, int *width, int *height) override;
-    bool onDecodeSubset(SkBitmap* bitmap, const SkIRect& region) override;
-#endif
     Result onDecode(SkStream* stream, SkBitmap* bm, Mode) override;
 
 private:
@@ -126,16 +122,6 @@ static void sk_read_fn(png_structp png_ptr, png_bytep data, png_size_t length) {
     }
 }
 
-#ifdef SK_PNG_INDEX_SUPPORTED
-static void sk_seek_fn(png_structp png_ptr, png_uint_32 offset) {
-    SkStreamRewindable* sk_stream = (SkStreamRewindable*) png_get_io_ptr(png_ptr);
-    if (!sk_stream->rewind()) {
-        png_error(png_ptr, "Failed to rewind stream!");
-    }
-    (void)sk_stream->skip(offset);
-}
-#endif
-
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
 static int sk_read_user_chunk(png_structp png_ptr, png_unknown_chunkp chunk) {
     SkImageDecoder::Peeker* peeker =
@@ -256,9 +242,6 @@ bool SkPNGImageDecoder::onDecodeInit(SkStream* sk_stream, png_structp *png_ptrp,
     * png_init_io() here you would call:
     */
     png_set_read_fn(png_ptr, (void *)sk_stream, sk_read_fn);
-#ifdef SK_PNG_INDEX_SUPPORTED
-    png_set_seek_fn(png_ptr, sk_seek_fn);
-#endif
     /* 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 */ );
@@ -720,267 +703,6 @@ bool SkPNGImageDecoder::decodePalette(png_structp png_ptr, png_infop info_ptr,
     return true;
 }
 
-#ifdef SK_PNG_INDEX_SUPPORTED
-
-bool SkPNGImageDecoder::onBuildTileIndex(SkStreamRewindable* sk_stream, int *width, int *height) {
-    SkAutoTDelete<SkStreamRewindable> streamDeleter(sk_stream);
-    png_structp png_ptr;
-    png_infop   info_ptr;
-
-    if (!onDecodeInit(sk_stream, &png_ptr, &info_ptr)) {
-        return false;
-    }
-
-    if (setjmp(png_jmpbuf(png_ptr)) != 0) {
-        png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
-        return false;
-    }
-
-    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);
-
-    *width = origWidth;
-    *height = origHeight;
-
-    png_build_index(png_ptr);
-
-    if (fImageIndex) {
-        delete fImageIndex;
-    }
-    fImageIndex = new SkPNGImageIndex(streamDeleter.detach(), png_ptr, info_ptr);
-
-    return true;
-}
-
-bool SkPNGImageDecoder::onDecodeSubset(SkBitmap* bm, const SkIRect& region) {
-    if (nullptr == fImageIndex) {
-        return false;
-    }
-
-    png_structp png_ptr = fImageIndex->fPng_ptr;
-    png_infop info_ptr = fImageIndex->fInfo_ptr;
-    if (setjmp(png_jmpbuf(png_ptr))) {
-        return false;
-    }
-
-    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);
-
-    SkIRect rect = SkIRect::MakeWH(origWidth, origHeight);
-
-    if (!rect.intersect(region)) {
-        // If the requested region is entirely outside the image, just
-        // returns false
-        return false;
-    }
-
-    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 false;
-    }
-
-    const int sampleSize = this->getSampleSize();
-    SkScaledBitmapSampler sampler(origWidth, rect.height(), sampleSize);
-
-    SkBitmap decodedBitmap;
-    decodedBitmap.setInfo(SkImageInfo::Make(sampler.scaledWidth(), sampler.scaledHeight(),
-                                            colorType, kPremul_SkAlphaType));
-
-    // 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);
-
-    // Check ahead of time if the swap(dest, src) is possible.
-    // If yes, then we will stick to AllocPixelRef since it's cheaper with the swap happening.
-    // If no, then we will use alloc to allocate pixels to prevent garbage collection.
-    int w = rect.width() / sampleSize;
-    int h = rect.height() / sampleSize;
-    const bool swapOnly = (rect == region) && (w == decodedBitmap.width()) &&
-                          (h == decodedBitmap.height()) && bm->isNull();
-    const bool needColorTable = kIndex_8_SkColorType == colorType;
-    if (swapOnly) {
-        if (!this->allocPixelRef(&decodedBitmap, needColorTable ? colorTable : nullptr)) {
-            return false;
-        }
-    } else {
-        if (!decodedBitmap.tryAllocPixels(nullptr, needColorTable ? colorTable : nullptr)) {
-            return false;
-        }
-    }
-    SkAutoLockPixels alp(decodedBitmap);
-
-    /* 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).
-    */
-
-    // Direct access to png_ptr fields is deprecated in libpng > 1.2.
-#if defined(PNG_1_0_X) || defined (PNG_1_2_X)
-    png_ptr->pass = 0;
-#else
-    // FIXME: This sets pass as desired, but also sets iwidth. Is that ok?
-    png_set_interlaced_pass(png_ptr, 0);
-#endif
-    png_read_update_info(png_ptr, info_ptr);
-
-    int actualTop = rect.fTop;
-
-    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++) {
-            png_configure_decoder(png_ptr, &actualTop, i);
-            for (int j = 0; j < rect.fTop - actualTop; j++) {
-                uint8_t* bmRow = decodedBitmap.getAddr8(0, 0);
-                png_read_rows(png_ptr, &bmRow, png_bytepp_NULL, 1);
-            }
-            png_uint_32 bitmapHeight = (png_uint_32) decodedBitmap.height();
-            for (png_uint_32 y = 0; y < bitmapHeight; 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 false;
-        }
-        const int height = decodedBitmap.height();
-
-        if (number_passes > 1) {
-            SkAutoMalloc storage(origWidth * origHeight * srcBytesPerPixel);
-            uint8_t* base = (uint8_t*)storage.get();
-            size_t rb = origWidth * srcBytesPerPixel;
-
-            for (int i = 0; i < number_passes; i++) {
-                png_configure_decoder(png_ptr, &actualTop, i);
-                for (int j = 0; j < rect.fTop - actualTop; j++) {
-                    png_read_rows(png_ptr, &base, png_bytepp_NULL, 1);
-                }
-                uint8_t* row = base;
-                for (int32_t y = 0; y < rect.height(); y++) {
-                    uint8_t* bmRow = row;
-                    png_read_rows(png_ptr, &bmRow, png_bytepp_NULL, 1);
-                    row += rb;
-                }
-            }
-            // now sample it
-            base += sampler.srcY0() * rb;
-            for (int y = 0; y < height; y++) {
-                reallyHasAlpha |= sampler.next(base);
-                base += sampler.srcDY() * rb;
-            }
-        } else {
-            SkAutoMalloc storage(origWidth * srcBytesPerPixel);
-            uint8_t* srcRow = (uint8_t*)storage.get();
-
-            png_configure_decoder(png_ptr, &actualTop, 0);
-            skip_src_rows(png_ptr, srcRow, sampler.srcY0());
-
-            for (int i = 0; i < rect.fTop - actualTop; i++) {
-                png_read_rows(png_ptr, &srcRow, png_bytepp_NULL, 1);
-            }
-            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);
-                }
-            }
-        }
-    }
-
-    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 colortypess.
-                return false;
-            default: {
-                // Fall through to finish the decode. This config either
-                // supports unpremul or it is irrelevant because it has no
-                // alpha (or only alpha).
-                // These brackets prevent a warning.
-            }
-        }
-    }
-    SkAlphaType alphaType = kOpaque_SkAlphaType;
-    if (reallyHasAlpha) {
-        if (this->getRequireUnpremultipliedColors()) {
-            alphaType = kUnpremul_SkAlphaType;
-        } else {
-            alphaType = kPremul_SkAlphaType;
-        }
-    }
-    decodedBitmap.setAlphaType(alphaType);
-
-    if (swapOnly) {
-        bm->swap(decodedBitmap);
-        return true;
-    }
-    return this->cropBitmap(bm, &decodedBitmap, sampleSize, region.x(), region.y(),
-                            region.width(), region.height(), 0, rect.y());
-}
-#endif
-
 ///////////////////////////////////////////////////////////////////////////////
 
 #include "SkColorPriv.h"