Remove SkEncodedInfo kUnknown_Color and kUnknown_Alpha from public API

src/codec/SkPngCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
@@ skipping 243 matching lines @@
 
 #endif // LIBPNG >= 1.6
 
     // Finally, what should we do if there is no color space information in the PNG?
     // The specification says that this indicates "gamma is unknown" and that the
     // "color is device dependent".  I'm assuming we can represent this with NULL.
     // But should we guess sRGB?  Most images are sRGB, even if they don't specify.
     return nullptr;
 }
 
+static int bytes_per_pixel(int bitsPerPixel) {

[scroggo, 2016/04/25 15:10:43]

Before I scan this 200 line block line by line to see if anything changed, did
anything change? Or is this just a move?

[msarett, 2016/04/25 15:18:21]

Sorry I should I have mentioned - yes this is all a move.

I made changes to read_header() and NewFromStream.

+    // Note that we will have to change this implementation if we start
+    // supporting outputs from libpng that are less than 8-bits per component.
+    return bitsPerPixel / 8;
+}
+
+// Subclass of SkPngCodec which supports scanline decoding
+class SkPngScanlineDecoder : public SkPngCodec {
+public:
+    SkPngScanlineDecoder(int width, int height, const SkEncodedInfo& info, SkStream* stream,
+            SkPngChunkReader* chunkReader, png_structp png_ptr, png_infop info_ptr, int bitDepth,
+            sk_sp<SkColorSpace> colorSpace)
+        : INHERITED(width, height, info, stream, chunkReader, png_ptr, info_ptr, bitDepth, 1,
+                    colorSpace)
+        , fSrcRow(nullptr)
+    {}
+
+    Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
+            SkPMColor ctable[], int* ctableCount) override {
+        if (!conversion_possible(dstInfo, this->getInfo())) {
+            return kInvalidConversion;
+        }
+
+        const Result result = this->initializeSwizzler(dstInfo, options, ctable,
+                                                       ctableCount);
+        if (result != kSuccess) {
+            return result;
+        }
+
+        fStorage.reset(this->getInfo().width() *
+                (bytes_per_pixel(this->getEncodedInfo().bitsPerPixel())));
+        fSrcRow = fStorage.get();
+
+        return kSuccess;
+    }
+
+    int onGetScanlines(void* dst, int count, size_t rowBytes) override {
+        // Assume that an error in libpng indicates an incomplete input.
+        int row = 0;
+        if (setjmp(png_jmpbuf(this->png_ptr()))) {
+            SkCodecPrintf("setjmp long jump!\n");
+            return row;
+        }
+
+        void* dstRow = dst;
+        for (; row < count; row++) {
+            png_read_row(this->png_ptr(), fSrcRow, nullptr);
+            this->swizzler()->swizzle(dstRow, fSrcRow);
+            dstRow = SkTAddOffset<void>(dstRow, rowBytes);
+        }
+
+        return row;
+    }
+
+    bool onSkipScanlines(int count) override {
+        // Assume that an error in libpng indicates an incomplete input.
+        if (setjmp(png_jmpbuf(this->png_ptr()))) {
+            SkCodecPrintf("setjmp long jump!\n");
+            return false;
+        }
+
+        for (int row = 0; row < count; row++) {
+            png_read_row(this->png_ptr(), fSrcRow, nullptr);
+        }
+        return true;
+    }
+
+private:
+    SkAutoTMalloc<uint8_t>      fStorage;
+    uint8_t*                    fSrcRow;
+
+    typedef SkPngCodec INHERITED;
+};
+
+
+class SkPngInterlacedScanlineDecoder : public SkPngCodec {
+public:
+    SkPngInterlacedScanlineDecoder(int width, int height, const SkEncodedInfo& info,
+            SkStream* stream, SkPngChunkReader* chunkReader, png_structp png_ptr,
+            png_infop info_ptr, int bitDepth, int numberPasses, sk_sp<SkColorSpace> colorSpace)
+        : INHERITED(width, height, info, stream, chunkReader, png_ptr, info_ptr, bitDepth,
+                    numberPasses, colorSpace)
+        , fHeight(-1)
+        , fCanSkipRewind(false)
+    {
+        SkASSERT(numberPasses != 1);
+    }
+
+    Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
+            SkPMColor ctable[], int* ctableCount) override {
+        if (!conversion_possible(dstInfo, this->getInfo())) {
+            return kInvalidConversion;
+        }
+
+        const Result result = this->initializeSwizzler(dstInfo, options, ctable,
+                                                       ctableCount);
+        if (result != kSuccess) {
+            return result;
+        }
+
+        fHeight = dstInfo.height();
+        // FIXME: This need not be called on a second call to onStartScanlineDecode.
+        fSrcRowBytes = this->getInfo().width() *
+                (bytes_per_pixel(this->getEncodedInfo().bitsPerPixel()));
+        fGarbageRow.reset(fSrcRowBytes);
+        fGarbageRowPtr = static_cast<uint8_t*>(fGarbageRow.get());
+        fCanSkipRewind = true;
+
+        return SkCodec::kSuccess;
+    }
+
+    int onGetScanlines(void* dst, int count, size_t dstRowBytes) override {
+        // rewind stream if have previously called onGetScanlines,
+        // since we need entire progressive image to get scanlines
+        if (fCanSkipRewind) {
+            // We already rewound in onStartScanlineDecode, so there is no reason to rewind.
+            // Next time onGetScanlines is called, we will need to rewind.
+            fCanSkipRewind = false;
+        } else {
+            // rewindIfNeeded resets fCurrScanline, since it assumes that start
+            // needs to be called again before scanline decoding. PNG scanline
+            // decoding is the exception, since it needs to rewind between
+            // calls to getScanlines. Keep track of fCurrScanline, to undo the
+            // reset.
+            const int currScanline = this->nextScanline();
+            // This method would never be called if currScanline is -1
+            SkASSERT(currScanline != -1);
+
+            if (!this->rewindIfNeeded()) {
+                return kCouldNotRewind;
+            }
+            this->updateCurrScanline(currScanline);
+        }
+
+        if (setjmp(png_jmpbuf(this->png_ptr()))) {
+            SkCodecPrintf("setjmp long jump!\n");
+            // FIXME (msarett): Returning 0 is pessimistic.  If we can complete a single pass,
+            // we may be able to report that all of the memory has been initialized.  Even if we
+            // fail on the first pass, we can still report than some scanlines are initialized.
+            return 0;
+        }
+        SkAutoTMalloc<uint8_t> storage(count * fSrcRowBytes);
+        uint8_t* storagePtr = storage.get();
+        uint8_t* srcRow;
+        const int startRow = this->nextScanline();
+        for (int i = 0; i < this->numberPasses(); i++) {
+            // read rows we planned to skip into garbage row
+            for (int y = 0; y < startRow; y++){
+                png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
+            }
+            // read rows we care about into buffer
+            srcRow = storagePtr;
+            for (int y = 0; y < count; y++) {
+                png_read_row(this->png_ptr(), srcRow, nullptr);
+                srcRow += fSrcRowBytes;
+            }
+            // read rows we don't want into garbage buffer
+            for (int y = 0; y < fHeight - startRow - count; y++) {
+                png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
+            }
+        }
+        //swizzle the rows we care about
+        srcRow = storagePtr;
+        void* dstRow = dst;
+        for (int y = 0; y < count; y++) {
+            this->swizzler()->swizzle(dstRow, srcRow);
+            dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
+            srcRow += fSrcRowBytes;
+        }
+
+        return count;
+    }
+
+    bool onSkipScanlines(int count) override {
+        // The non-virtual version will update fCurrScanline.
+        return true;
+    }
+
+    SkScanlineOrder onGetScanlineOrder() const override {
+        return kNone_SkScanlineOrder;
+    }
+
+private:
+    int                         fHeight;
+    size_t                      fSrcRowBytes;
+    SkAutoMalloc                fGarbageRow;
+    uint8_t*                    fGarbageRowPtr;
+    // FIXME: This imitates behavior in SkCodec::rewindIfNeeded. That function
+    // is called whenever some action is taken that reads the stream and
+    // therefore the next call will require a rewind. So it modifies a boolean
+    // to note that the *next* time it is called a rewind is needed.
+    // SkPngInterlacedScanlineDecoder has an extra wrinkle - calling
+    // onStartScanlineDecode followed by onGetScanlines does *not* require a
+    // rewind. Since rewindIfNeeded does not have this flexibility, we need to
+    // add another layer.
+    bool                        fCanSkipRewind;
+
+    typedef SkPngCodec INHERITED;
+};
+
 // Reads the header and initializes the output fields, if not NULL.
 //
 // @param stream Input data. Will be read to get enough information to properly
 //      setup the codec.
 // @param chunkReader SkPngChunkReader, for reading unknown chunks. May be NULL.
 //      If not NULL, png_ptr will hold an *unowned* pointer to it. The caller is
 //      expected to continue to own it for the lifetime of the png_ptr.
+// @param outCodec Optional output variable.  If non-NULL, will be set to a new
+//      SkPngCodec on success.
 // @param png_ptrp Optional output variable. If non-NULL, will be set to a new
 //      png_structp on success.
 // @param info_ptrp Optional output variable. If non-NULL, will be set to a new
 //      png_infop on success;
-// @param info Optional output variable. If non-NULL, will be set to
-//      reflect the properties of the encoded image on success.
-// @param bitDepthPtr Optional output variable. If non-NULL, will be set to the
-//      bit depth of the encoded image on success.
-// @param numberPassesPtr Optional output variable. If non-NULL, will be set to
-//      the number_passes of the encoded image on success.
 // @return true on success, in which case the caller is responsible for calling
 //      png_destroy_read_struct(png_ptrp, info_ptrp).
 //      If it returns false, the passed in fields (except stream) are unchanged.
-static bool read_header(SkStream* stream, SkPngChunkReader* chunkReader,
-                        png_structp* png_ptrp, png_infop* info_ptrp,
-                        int* width, int* height, SkEncodedInfo* info, int* bitDepthPtr,
-                        int* numberPassesPtr) {
+static bool read_header(SkStream* stream, SkPngChunkReader* chunkReader, SkCodec** outCodec,
+                        png_structp* png_ptrp, png_infop* info_ptrp) {
     // The image is known to be a PNG. Decode enough to know the SkImageInfo.
     png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr,
                                                  sk_error_fn, sk_warning_fn);
     if (!png_ptr) {
         return false;
     }
 
     AutoCleanPng autoClean(png_ptr);
 
     png_infop info_ptr = png_create_info_struct(png_ptr);
@@ skipping 22 matching lines @@
 #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, encodedColorType;
     png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bitDepth,
                  &encodedColorType, nullptr, nullptr, nullptr);
 
-    if (bitDepthPtr) {
-        *bitDepthPtr = bitDepth;
-    }
-
     // Tell libpng to strip 16 bit/color files down to 8 bits/color.
     // TODO: Should we handle this in SkSwizzler?  Could this also benefit
     //       RAW decodes?
     if (bitDepth == 16) {
         SkASSERT(PNG_COLOR_TYPE_PALETTE != encodedColorType);
         png_set_strip_16(png_ptr);
     }
 
     // Now determine the default colorType and alphaType and set the required transforms.
     // Often, we depend on SkSwizzler to perform any transforms that we need.  However, we
@@ skipping 50 matching lines @@
             alpha = SkEncodedInfo::kUnpremul_Alpha;
             break;
         default:
             // All the color types have been covered above.
             SkASSERT(false);
             color = SkEncodedInfo::kRGBA_Color;
             alpha = SkEncodedInfo::kUnpremul_Alpha;
     }
 
     int numberPasses = png_set_interlace_handling(png_ptr);
-    if (numberPassesPtr) {
-        *numberPassesPtr = numberPasses;
-    }
 
-    if (info) {
-        *info = SkEncodedInfo::Make(color, alpha, 8);
-    }
-    if (width) {
-        *width = origWidth;
-    }
-    if (height) {
-        *height = origHeight;
-    }
     autoClean.release();
     if (png_ptrp) {
         *png_ptrp = png_ptr;
     }
     if (info_ptrp) {
         *info_ptrp = info_ptr;
     }
 
+    if (outCodec) {
+        sk_sp<SkColorSpace> colorSpace = read_color_space(png_ptr, info_ptr);
+        SkEncodedInfo info = SkEncodedInfo::Make(color, alpha, 8);
+
+        if (1 == numberPasses) {
+            *outCodec = new SkPngScanlineDecoder(origWidth, origHeight, info, stream,
+                    chunkReader, png_ptr, info_ptr, bitDepth, colorSpace);
+        }
+
+        *outCodec = new SkPngInterlacedScanlineDecoder(origWidth, origHeight, info, stream,
+            chunkReader, png_ptr, info_ptr, bitDepth, numberPasses, colorSpace);
+    }
+
     return true;
 }
 
 SkPngCodec::SkPngCodec(int width, int height, const SkEncodedInfo& info, SkStream* stream,
                        SkPngChunkReader* chunkReader, png_structp png_ptr, png_infop info_ptr,
                        int bitDepth, int numberPasses, sk_sp<SkColorSpace> colorSpace)
     : INHERITED(width, height, info, stream, colorSpace)
     , fPngChunkReader(SkSafeRef(chunkReader))
     , fPng_ptr(png_ptr)
     , fInfo_ptr(info_ptr)
@@ skipping 54 matching lines @@
 bool SkPngCodec::onRewind() {
     // This sets fPng_ptr and fInfo_ptr to nullptr. If read_header
     // succeeds, they will be repopulated, and if it fails, they will
     // remain nullptr. Any future accesses to fPng_ptr and fInfo_ptr will
     // come through this function which will rewind and again attempt
     // to reinitialize them.
     this->destroyReadStruct();
 
     png_structp png_ptr;
     png_infop info_ptr;
-    if (!read_header(this->stream(), fPngChunkReader.get(), &png_ptr, &info_ptr,
-                     nullptr, nullptr, nullptr, nullptr, nullptr)) {
+    if (!read_header(this->stream(), fPngChunkReader.get(), nullptr, &png_ptr, &info_ptr)) {
         return false;
     }
 
     fPng_ptr = png_ptr;
     fInfo_ptr = info_ptr;
     return true;
 }
 
-static int bytes_per_pixel(int bitsPerPixel) {
-    // Note that we will have to change this implementation if we start
-    // supporting outputs from libpng that are less than 8-bits per component.
-    return bitsPerPixel / 8;
-}
-
 SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void* dst,
                                         size_t dstRowBytes, const Options& options,
                                         SkPMColor ctable[], int* ctableCount,
                                         int* rowsDecoded) {
     if (!conversion_possible(requestedInfo, this->getInfo())) {
         return kInvalidConversion;
     }
     if (options.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
@@ skipping 74 matching lines @@
 }
 
 uint32_t SkPngCodec::onGetFillValue(SkColorType colorType) const {
     const SkPMColor* colorPtr = get_color_ptr(fColorTable.get());
     if (colorPtr) {
         return get_color_table_fill_value(colorType, colorPtr, 0);
     }
     return INHERITED::onGetFillValue(colorType);
 }
 
-// Subclass of SkPngCodec which supports scanline decoding
-class SkPngScanlineDecoder : public SkPngCodec {
-public:
-    SkPngScanlineDecoder(int width, int height, const SkEncodedInfo& info, SkStream* stream,
-            SkPngChunkReader* chunkReader, png_structp png_ptr, png_infop info_ptr, int bitDepth,
-            sk_sp<SkColorSpace> colorSpace)
-        : INHERITED(width, height, info, stream, chunkReader, png_ptr, info_ptr, bitDepth, 1,
-                    colorSpace)
-        , fSrcRow(nullptr)
-    {}
+SkCodec* SkPngCodec::NewFromStream(SkStream* stream, SkPngChunkReader* chunkReader) {
+    SkAutoTDelete<SkStream> streamDeleter(stream);
 
-    Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
-            SkPMColor ctable[], int* ctableCount) override {
-        if (!conversion_possible(dstInfo, this->getInfo())) {
-            return kInvalidConversion;
-        }
-
-        const Result result = this->initializeSwizzler(dstInfo, options, ctable,
-                                                       ctableCount);
-        if (result != kSuccess) {
-            return result;
-        }
-
-        fStorage.reset(this->getInfo().width() *
-                (bytes_per_pixel(this->getEncodedInfo().bitsPerPixel())));
-        fSrcRow = fStorage.get();
-
-        return kSuccess;
+    SkCodec* outCodec;
+    if (read_header(stream, chunkReader, &outCodec, nullptr, nullptr)) {
+        // Codec has taken ownership of the stream.
+        SkASSERT(outCodec);
+        streamDeleter.release();
+        return outCodec;
     }
 
-    int onGetScanlines(void* dst, int count, size_t rowBytes) override {
-        // Assume that an error in libpng indicates an incomplete input.
-        int row = 0;
-        if (setjmp(png_jmpbuf(this->png_ptr()))) {
-            SkCodecPrintf("setjmp long jump!\n");
-            return row;
-        }
-
-        void* dstRow = dst;
-        for (; row < count; row++) {
-            png_read_row(this->png_ptr(), fSrcRow, nullptr);
-            this->swizzler()->swizzle(dstRow, fSrcRow);
-            dstRow = SkTAddOffset<void>(dstRow, rowBytes);
-        }
-
-        return row;
-    }
-
-    bool onSkipScanlines(int count) override {
-        // Assume that an error in libpng indicates an incomplete input.
-        if (setjmp(png_jmpbuf(this->png_ptr()))) {
-            SkCodecPrintf("setjmp long jump!\n");
-            return false;
-        }
-
-        for (int row = 0; row < count; row++) {
-            png_read_row(this->png_ptr(), fSrcRow, nullptr);
-        }
-        return true;
-    }
-
-private:
-    SkAutoTMalloc<uint8_t>      fStorage;
-    uint8_t*                    fSrcRow;
-
-    typedef SkPngCodec INHERITED;
-};
-
-
-class SkPngInterlacedScanlineDecoder : public SkPngCodec {
-public:
-    SkPngInterlacedScanlineDecoder(int width, int height, const SkEncodedInfo& info,
-            SkStream* stream, SkPngChunkReader* chunkReader, png_structp png_ptr,
-            png_infop info_ptr, int bitDepth, int numberPasses, sk_sp<SkColorSpace> colorSpace)
-        : INHERITED(width, height, info, stream, chunkReader, png_ptr, info_ptr, bitDepth,
-                    numberPasses, colorSpace)
-        , fHeight(-1)
-        , fCanSkipRewind(false)
-    {
-        SkASSERT(numberPasses != 1);
-    }
-
-    Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& options,
-            SkPMColor ctable[], int* ctableCount) override {
-        if (!conversion_possible(dstInfo, this->getInfo())) {
-            return kInvalidConversion;
-        }
-
-        const Result result = this->initializeSwizzler(dstInfo, options, ctable,
-                                                       ctableCount);
-        if (result != kSuccess) {
-            return result;
-        }
-
-        fHeight = dstInfo.height();
-        // FIXME: This need not be called on a second call to onStartScanlineDecode.
-        fSrcRowBytes = this->getInfo().width() *
-                (bytes_per_pixel(this->getEncodedInfo().bitsPerPixel()));
-        fGarbageRow.reset(fSrcRowBytes);
-        fGarbageRowPtr = static_cast<uint8_t*>(fGarbageRow.get());
-        fCanSkipRewind = true;
-
-        return SkCodec::kSuccess;
-    }
-
-    int onGetScanlines(void* dst, int count, size_t dstRowBytes) override {
-        // rewind stream if have previously called onGetScanlines,
-        // since we need entire progressive image to get scanlines
-        if (fCanSkipRewind) {
-            // We already rewound in onStartScanlineDecode, so there is no reason to rewind.
-            // Next time onGetScanlines is called, we will need to rewind.
-            fCanSkipRewind = false;
-        } else {
-            // rewindIfNeeded resets fCurrScanline, since it assumes that start
-            // needs to be called again before scanline decoding. PNG scanline
-            // decoding is the exception, since it needs to rewind between
-            // calls to getScanlines. Keep track of fCurrScanline, to undo the
-            // reset.
-            const int currScanline = this->nextScanline();
-            // This method would never be called if currScanline is -1
-            SkASSERT(currScanline != -1);
-
-            if (!this->rewindIfNeeded()) {
-                return kCouldNotRewind;
-            }
-            this->updateCurrScanline(currScanline);
-        }
-
-        if (setjmp(png_jmpbuf(this->png_ptr()))) {
-            SkCodecPrintf("setjmp long jump!\n");
-            // FIXME (msarett): Returning 0 is pessimistic.  If we can complete a single pass,
-            // we may be able to report that all of the memory has been initialized.  Even if we
-            // fail on the first pass, we can still report than some scanlines are initialized.
-            return 0;
-        }
-        SkAutoTMalloc<uint8_t> storage(count * fSrcRowBytes);
-        uint8_t* storagePtr = storage.get();
-        uint8_t* srcRow;
-        const int startRow = this->nextScanline();
-        for (int i = 0; i < this->numberPasses(); i++) {
-            // read rows we planned to skip into garbage row
-            for (int y = 0; y < startRow; y++){
-                png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
-            }
-            // read rows we care about into buffer
-            srcRow = storagePtr;
-            for (int y = 0; y < count; y++) {
-                png_read_row(this->png_ptr(), srcRow, nullptr);
-                srcRow += fSrcRowBytes;
-            }
-            // read rows we don't want into garbage buffer
-            for (int y = 0; y < fHeight - startRow - count; y++) {
-                png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
-            }
-        }
-        //swizzle the rows we care about
-        srcRow = storagePtr;
-        void* dstRow = dst;
-        for (int y = 0; y < count; y++) {
-            this->swizzler()->swizzle(dstRow, srcRow);
-            dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
-            srcRow += fSrcRowBytes;
-        }
-
-        return count;
-    }
-
-    bool onSkipScanlines(int count) override {
-        // The non-virtual version will update fCurrScanline.
-        return true;
-    }
-
-    SkScanlineOrder onGetScanlineOrder() const override {
-        return kNone_SkScanlineOrder;
-    }
-
-private:
-    int                         fHeight;
-    size_t                      fSrcRowBytes;
-    SkAutoMalloc                fGarbageRow;
-    uint8_t*                    fGarbageRowPtr;
-    // FIXME: This imitates behavior in SkCodec::rewindIfNeeded. That function
-    // is called whenever some action is taken that reads the stream and
-    // therefore the next call will require a rewind. So it modifies a boolean
-    // to note that the *next* time it is called a rewind is needed.
-    // SkPngInterlacedScanlineDecoder has an extra wrinkle - calling
-    // onStartScanlineDecode followed by onGetScanlines does *not* require a
-    // rewind. Since rewindIfNeeded does not have this flexibility, we need to
-    // add another layer.
-    bool                        fCanSkipRewind;
-
-    typedef SkPngCodec INHERITED;
-};
-
-SkCodec* SkPngCodec::NewFromStream(SkStream* stream, SkPngChunkReader* chunkReader) {
-    SkAutoTDelete<SkStream> streamDeleter(stream);
-    png_structp png_ptr;
-    png_infop info_ptr;
-    int width, height;
-    SkEncodedInfo imageInfo;
-    int bitDepth;
-    int numberPasses;
-
-    if (!read_header(stream, chunkReader, &png_ptr, &info_ptr, &width, &height, &imageInfo,
-                     &bitDepth, &numberPasses)) {
-        return nullptr;
-    }
-
-    auto colorSpace = read_color_space(png_ptr, info_ptr);
-
-    if (1 == numberPasses) {
-        return new SkPngScanlineDecoder(width, height, imageInfo, streamDeleter.release(),
-                                        chunkReader, png_ptr, info_ptr, bitDepth, colorSpace);
-    }
-
-    return new SkPngInterlacedScanlineDecoder(width, height, imageInfo, streamDeleter.release(),
-                                              chunkReader, png_ptr, info_ptr, bitDepth,
-                                              numberPasses, colorSpace);
+    return nullptr;
 }