Create an SkAndroidCodec API separate from SkCodec

src/codec/SkScaledCodec.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 "SkCodec.h"
 #include "SkCodecPriv.h"
-#include "SkScaledCodec.h"
-#include "SkStream.h"
-#include "SkWebpCodec.h"
-
-
-SkCodec* SkScaledCodec::NewFromStream(SkStream* stream) {
-    SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream));
-    if (nullptr == codec) {
-        return nullptr;
-    }
-
-    switch (codec->getEncodedFormat()) {
-        case kWEBP_SkEncodedFormat:
-            // Webp codec supports scaling and subsetting natively
-            return codec.detach();
-        case kPNG_SkEncodedFormat:
-        case kJPEG_SkEncodedFormat:
-            // wrap in new SkScaledCodec
-            return new SkScaledCodec(codec.detach());
-        default:
-            // FIXME: SkScaledCodec is temporarily disabled for other formats
-            // while focusing on the formats that are supported by
-            // BitmapRegionDecoder.
-            return nullptr;
-    }
-}
-
-SkCodec* SkScaledCodec::NewFromData(SkData* data) {
-    if (!data) {
-        return nullptr;
-    }
-    return NewFromStream(new SkMemoryStream(data));
-}
-
-SkScaledCodec::SkScaledCodec(SkCodec* codec)
-    : INHERITED(codec->getInfo(), nullptr)
+#include "SkSampledCodec.h"
+
+// FIXME: Rename this file to SkSampledCodec.cpp
+
+SkSampledCodec::SkSampledCodec(SkCodec* codec)
+    : INHERITED(codec->getInfo())
     , fCodec(codec)
 {}
 
-SkScaledCodec::~SkScaledCodec() {}
-
-bool SkScaledCodec::onRewind() {
-    return fCodec->onRewind();
-}
-
-static SkISize best_scaled_dimensions(const SkISize& origDims, const SkISize& nativeDims,
-                                      const SkISize& scaledCodecDims, float desiredScale) {
-    if (nativeDims == scaledCodecDims) {
-        // does not matter which to return if equal. Return here to skip below calculations
-        return nativeDims;
-    }
-    float idealWidth = origDims.width() * desiredScale;
-    float idealHeight = origDims.height() * desiredScale;
-
-    // calculate difference between native dimensions and ideal dimensions
-    float nativeWDiff = SkTAbs(idealWidth - nativeDims.width());
-    float nativeHDiff = SkTAbs(idealHeight - nativeDims.height());
-    float nativeDiff = nativeWDiff + nativeHDiff;
-
+SkISize SkSampledCodec::onGetSampledDimensions(int sampleSize) const {
+    // Fast path for when we are not scaling.
+    if (1 == sampleSize) {
+        return fCodec->getInfo().dimensions();
+    }
+
+    const int width = fCodec->getInfo().width();
+    const int height = fCodec->getInfo().height();
+
+    // Check if the codec can provide the scaling natively.
+    float scale = get_scale_from_sample_size(sampleSize);
+    SkSize idealSize = SkSize::Make(scale * (float) width, scale * (float) height);
+    SkISize nativeSize = fCodec->getScaledDimensions(scale);
+    float widthDiff = SkTAbs(((float) nativeSize.width()) - idealSize.width());
+    float heightDiff = SkTAbs(((float) nativeSize.height()) - idealSize.height());
     // Native scaling is preferred to sampling.  If we can scale natively to
     // within one of the ideal value, we should choose to scale natively.
-    if (nativeWDiff < 1.0f && nativeHDiff < 1.0f) {
-        return nativeDims;
-    }
-
-    // calculate difference between scaledCodec dimensions and ideal dimensions
-    float scaledCodecWDiff = SkTAbs(idealWidth - scaledCodecDims.width());
-    float scaledCodecHDiff = SkTAbs(idealHeight - scaledCodecDims.height());
-    float scaledCodecDiff = scaledCodecWDiff + scaledCodecHDiff;
-
-    // return dimensions closest to ideal dimensions.
-    // If the differences are equal, return nativeDims, as native scaling is more efficient.
-    return nativeDiff > scaledCodecDiff ? scaledCodecDims : nativeDims;
+    if (widthDiff < 1.0f && heightDiff < 1.0f) {
+        return nativeSize;
+    }
+
+    // Provide the scaling by sampling.
+    return SkISize::Make(get_scaled_dimension(width, sampleSize),
+            get_scaled_dimension(height, sampleSize));
 }
 
-/*
- * Return a valid set of output dimensions for this decoder, given an input scale
- */
-SkISize SkScaledCodec::onGetScaledDimensions(float desiredScale) const {
-    SkISize nativeDimensions = fCodec->getScaledDimensions(desiredScale);
-    // support scaling down by integer numbers. Ex: 1/2, 1/3, 1/4 ...
-    SkISize scaledCodecDimensions;
-    if (desiredScale > 0.5f) {
-        // sampleSize = 1
-        scaledCodecDimensions = fCodec->getInfo().dimensions();
-    }
-    // sampleSize determines the step size between samples
-    // Ex: sampleSize = 2, sample every second pixel in x and y directions
-    int sampleSize = int ((1.0f / desiredScale) + 0.5f);
-
-    int scaledWidth = get_scaled_dimension(this->getInfo().width(), sampleSize);
-    int scaledHeight = get_scaled_dimension(this->getInfo().height(), sampleSize);
-
-    // Return the calculated output dimensions for the given scale
-    scaledCodecDimensions = SkISize::Make(scaledWidth, scaledHeight);
-
-    return best_scaled_dimensions(this->getInfo().dimensions(), nativeDimensions,
-                                  scaledCodecDimensions, desiredScale);
+SkCodec::Result SkSampledCodec::onGetAndroidPixels(const SkImageInfo& info, void* pixels,
+        size_t rowBytes, AndroidOptions& options) {
+    // Create an Options struct for the codec.
+    SkCodec::Options codecOptions;
+    codecOptions.fZeroInitialized = options.fZeroInitialized;
+
+    SkIRect* subset = options.fSubset;
+    if (!subset || subset->size() == fCodec->getInfo().dimensions()) {
+        if (fCodec->dimensionsSupported(info.dimensions())) {
+            return fCodec->getPixels(info, pixels, rowBytes, &codecOptions, options.fColorPtr,
+                    options.fColorCount);
+        }
+
+        // If the native codec does not support the requested scale, scale by sampling.
+        return this->sampledDecode(info, pixels, rowBytes, options);
+    }
+
+    // We are performing a subset decode.
+    int sampleSize = options.fSampleSize;
+    SkISize scaledSize = this->onGetSampledDimensions(sampleSize);
+    if (!fCodec->dimensionsSupported(scaledSize)) {
+        // If the native codec does not support the requested scale, scale by sampling.
+        return this->sampledDecode(info, pixels, rowBytes, options);
+    }
+
+    // Calculate the scaled subset bounds.
+    int scaledSubsetX = subset->x() / sampleSize;
+    int scaledSubsetY = subset->y() / sampleSize;
+    int scaledSubsetWidth = info.width();
+    int scaledSubsetHeight = info.height();
+
+    // Start the scanline decode.
+    SkIRect scanlineSubset = SkIRect::MakeXYWH(scaledSubsetX, 0, scaledSubsetWidth,
+            scaledSize.height());
+    codecOptions.fSubset = &scanlineSubset;
+    SkCodec::Result result = fCodec->startScanlineDecode(info.makeWH(scaledSize.width(),
+            scaledSize.height()), &codecOptions, options.fColorPtr, options.fColorCount);
+    if (SkCodec::kSuccess != result) {
+        return result;
+    }
+
+    // At this point, we are only concerned with subsetting.  Either no scale was
+    // requested, or the fCodec is handling the scale.
+    switch (fCodec->getScanlineOrder()) {
+        case SkCodec::kTopDown_SkScanlineOrder:
+        case SkCodec::kNone_SkScanlineOrder: {
+            if (!fCodec->skipScanlines(scaledSubsetY)) {
+                fCodec->fillIncompleteImage(info, pixels, rowBytes, options.fZeroInitialized,
+                        scaledSubsetHeight, 0);
+                return SkCodec::kIncompleteInput;
+            }
+
+            int decodedLines = fCodec->getScanlines(pixels, scaledSubsetHeight, rowBytes);
+            if (decodedLines != scaledSubsetHeight) {
+                return SkCodec::kIncompleteInput;
+            }
+            return SkCodec::kSuccess;
+        }
+        default:
+            SkASSERT(false);
+            return SkCodec::kUnimplemented;
+    }
 }
 
-// check if scaling to dstInfo size from srcInfo size using sampleSize is possible
-static bool scaling_supported(const SkISize& dstDim, const SkISize& srcDim,
-                              int* sampleX, int* sampleY) {
-    SkScaledCodec::ComputeSampleSize(dstDim, srcDim, sampleX, sampleY);
-    const int dstWidth = dstDim.width();
-    const int dstHeight = dstDim.height();
-    const int srcWidth = srcDim.width();
-    const int srcHeight = srcDim.height();
-     // only support down sampling, not up sampling
-    if (dstWidth > srcWidth || dstHeight  > srcHeight) {
-        return false;
-    }
-    // check that srcWidth is scaled down by an integer value
-    if (get_scaled_dimension(srcWidth, *sampleX) != dstWidth) {
-        return false;
-    }
-    // check that src height is scaled down by an integer value
-    if (get_scaled_dimension(srcHeight, *sampleY) != dstHeight) {
-        return false;
-    }
-    // sampleX and sampleY should be equal unless the original sampleSize requested was larger
-    // than srcWidth or srcHeight. If so, the result of this is dstWidth or dstHeight = 1.
-    // This functionality allows for tall thin images to still be scaled down by scaling factors.
-    if (*sampleX != *sampleY){
-        if (1 != dstWidth && 1 != dstHeight) {
-            return false;
-        }
-    }
-    return true;
-}
-
-bool SkScaledCodec::onDimensionsSupported(const SkISize& dim) {
-    // Check with fCodec first. No need to call the non-virtual version, which
-    // just checks if it matches the original, since a match means this method
-    // will not be called.
-    if (fCodec->onDimensionsSupported(dim)) {
-        return true;
-    }
-
-    // FIXME: These variables are unused, but are needed by scaling_supported.
-    // This class could also cache these values, and avoid calling this in
-    // onGetPixels (since getPixels already calls it).
-    int sampleX;
-    int sampleY;
-    return scaling_supported(dim, this->getInfo().dimensions(), &sampleX, &sampleY);
-}
-
-// calculates sampleSize in x and y direction
-void SkScaledCodec::ComputeSampleSize(const SkISize& dstDim, const SkISize& srcDim,
-                                      int* sampleXPtr, int* sampleYPtr) {
-    int srcWidth = srcDim.width();
-    int dstWidth = dstDim.width();
-    int srcHeight = srcDim.height();
-    int dstHeight = dstDim.height();
-
-    int sampleX = srcWidth / dstWidth;
-    int sampleY = srcHeight / dstHeight;
-
-    // only support down sampling, not up sampling
-    SkASSERT(dstWidth <= srcWidth);
-    SkASSERT(dstHeight <= srcHeight);
-
-    // sampleX and sampleY should be equal unless the original sampleSize requested was
-    // larger than srcWidth or srcHeight.
-    // If so, the result of this is dstWidth or dstHeight = 1. This functionality
-    // allows for tall thin images to still be scaled down by scaling factors.
-
-    if (sampleX != sampleY){
-        if (1 != dstWidth && 1 != dstHeight) {
-
-            // rounding during onGetScaledDimensions can cause different sampleSizes
-            // Ex: srcWidth = 79, srcHeight = 20, sampleSize = 10
-            // dstWidth = 7, dstHeight = 2, sampleX = 79/7 = 11, sampleY = 20/2 = 10
-            // correct for this rounding by comparing width to sampleY and height to sampleX
-
-            if (get_scaled_dimension(srcWidth, sampleY) == dstWidth) {
-                sampleX = sampleY;
-            } else if (get_scaled_dimension(srcHeight, sampleX) == dstHeight) {
-                sampleY = sampleX;
-            }
-        }
-    }
-
-    if (sampleXPtr) {
-        *sampleXPtr = sampleX;
-    }
-    if (sampleYPtr) {
-        *sampleYPtr = sampleY;
-    }
-}
-
-// TODO: Implement subsetting in onGetPixels which works when and when not sampling 
-
-SkCodec::Result SkScaledCodec::onGetPixels(const SkImageInfo& requestedInfo, void* dst,
-                                           size_t rowBytes, const Options& options,
-                                           SkPMColor ctable[], int* ctableCount,
-                                           int* rowsDecoded) {
-
+
+SkCodec::Result SkSampledCodec::sampledDecode(const SkImageInfo& info, void* pixels,
+        size_t rowBytes, AndroidOptions& options) {
+    // Create options struct for the codec.
+    SkCodec::Options sampledOptions;
+    sampledOptions.fZeroInitialized = options.fZeroInitialized;
+
+    // Check if there is a subset.
+    SkIRect subset;
+    int subsetY = 0;
+    int subsetWidth = fCodec->getInfo().width();
+    int subsetHeight = fCodec->getInfo().height();
     if (options.fSubset) {
-        // Subsets are not supported.
-        return kUnimplemented;
-    }
-
-    if (fCodec->dimensionsSupported(requestedInfo.dimensions())) {
-        // Make sure that the parent class does not fill on an incomplete decode, since
-        // fCodec will take care of filling the uninitialized lines.
-        *rowsDecoded = requestedInfo.height();
-        return fCodec->getPixels(requestedInfo, dst, rowBytes, &options, ctable, ctableCount);
-    }
-
-    // scaling requested
-    int sampleX;
-    int sampleY;
-    if (!scaling_supported(requestedInfo.dimensions(), fCodec->getInfo().dimensions(),
-                           &sampleX, &sampleY)) {
-        // onDimensionsSupported would have returned false, meaning we should never reach here.
-        SkASSERT(false);
-        return kInvalidScale;
-    }
-
-    // set first sample pixel in y direction
-    const int Y0 = get_start_coord(sampleY);
-
-    const int dstHeight = requestedInfo.height();
-    const int srcWidth = fCodec->getInfo().width();
-    const int srcHeight = fCodec->getInfo().height();
-
-    const SkImageInfo info = requestedInfo.makeWH(srcWidth, srcHeight);
-
-    Result result = fCodec->startScanlineDecode(info, &options, ctable, ctableCount);
-
-    if (kSuccess != result) {
+        // We will need to know about subsetting in the y-dimension in order to use the
+        // scanline decoder.
+        SkIRect* subsetPtr = options.fSubset;
+        subsetY = subsetPtr->y();
+        subsetWidth = subsetPtr->width();
+        subsetHeight = subsetPtr->height();
+
+        // The scanline decoder only needs to be aware of subsetting in the x-dimension.
+        subset.setXYWH(subsetPtr->x(), 0, subsetWidth, fCodec->getInfo().height());
+        sampledOptions.fSubset = &subset;
+    }
+
+    // Start the scanline decode.
+    SkCodec::Result result = fCodec->startScanlineDecode(
+            info.makeWH(fCodec->getInfo().width(), fCodec->getInfo().height()), &sampledOptions,
+            options.fColorPtr, options.fColorCount);
+    if (SkCodec::kSuccess != result) {
         return result;
     }
 
     SkSampler* sampler = fCodec->getSampler(true);
     if (!sampler) {
-        return kUnimplemented;
-    }
-
-    if (sampler->setSampleX(sampleX) != requestedInfo.width()) {
-        return kInvalidScale;
-    }
-
+        return SkCodec::kUnimplemented;
+    }
+
+    // Since we guarantee that output dimensions are always at least one (even if the sampleSize
+    // is greater than a given dimension), the input sampleSize is not always the sampleSize that
+    // we use in practice.
+    const int sampleX = subsetWidth / info.width();
+    const int sampleY = subsetHeight / info.height();
+    if (sampler->setSampleX(sampleX) != info.width()) {
+        return SkCodec::kInvalidScale;
+    }
+    if (get_scaled_dimension(subsetHeight, sampleY) != info.height()) {
+        return SkCodec::kInvalidScale;
+    }
+
+    const int samplingOffsetY = get_start_coord(sampleY);
+    const int startY = samplingOffsetY + subsetY;
+    int dstHeight = info.height();
     switch(fCodec->getScanlineOrder()) {
         case SkCodec::kTopDown_SkScanlineOrder: {
-            if (!fCodec->skipScanlines(Y0)) {
-                *rowsDecoded = 0;
-                return kIncompleteInput;
-            }
+            if (!fCodec->skipScanlines(startY)) {
+                fCodec->fillIncompleteImage(info, pixels, rowBytes, options.fZeroInitialized,
+                        dstHeight, 0);
+                return SkCodec::kIncompleteInput;
+            }
+            void* pixelPtr = pixels;
             for (int y = 0; y < dstHeight; y++) {
-                if (1 != fCodec->getScanlines(dst, 1, rowBytes)) {
-                    // The failed call to getScanlines() will take care of
-                    // filling the failed row, so we indicate that we have
-                    // decoded (y + 1) rows.
-                    *rowsDecoded = y + 1;
-                    return kIncompleteInput;
+                if (1 != fCodec->getScanlines(pixelPtr, 1, rowBytes)) {
+                    fCodec->fillIncompleteImage(info, pixels, rowBytes, options.fZeroInitialized,
+                            dstHeight, y + 1);
+                    return SkCodec::kIncompleteInput;
                 }
-                if (y < dstHeight - 1) {
-                    if (!fCodec->skipScanlines(sampleY - 1)) {
-                        *rowsDecoded = y + 1;
-                        return kIncompleteInput;
-                    }
+                int linesToSkip = SkTMin(sampleY - 1, dstHeight - y - 1);
+                if (!fCodec->skipScanlines(linesToSkip)) {
+                    fCodec->fillIncompleteImage(info, pixels, rowBytes, options.fZeroInitialized,
+                            dstHeight, y + 1);
+                    return SkCodec::kIncompleteInput;
                 }
-                dst = SkTAddOffset<void>(dst, rowBytes);
-            }
-            return kSuccess;
-        }
-        case SkCodec::kBottomUp_SkScanlineOrder:
-        case SkCodec::kOutOfOrder_SkScanlineOrder: {
-            Result result = kSuccess;
-            int y;
-            for (y = 0; y < srcHeight; y++) {
-                int srcY = fCodec->nextScanline();
-                if (is_coord_necessary(srcY, sampleY, dstHeight)) {
-                    void* dstPtr = SkTAddOffset<void>(dst, rowBytes * get_dst_coord(srcY, sampleY));
-                    if (1 != fCodec->getScanlines(dstPtr, 1, rowBytes)) {
-                        result = kIncompleteInput;
-                        break;
-                    }
-                } else {
-                    if (!fCodec->skipScanlines(1)) {
-                        result = kIncompleteInput;
-                        break;
-                    }
-                }
-            }
-
-            // We handle filling uninitialized memory here instead of in the parent class.
-            // The parent class does not know that we are sampling.
-            if (kIncompleteInput == result) {
-                const uint32_t fillValue = fCodec->getFillValue(requestedInfo.colorType(),
-                        requestedInfo.alphaType());
-                for (; y < srcHeight; y++) {
-                    int srcY = fCodec->outputScanline(y);
-                    if (is_coord_necessary(srcY, sampleY, dstHeight)) {
-                        void* dstRow = SkTAddOffset<void>(dst,
-                                rowBytes * get_dst_coord(srcY, sampleY));
-                        SkSampler::Fill(requestedInfo.makeWH(requestedInfo.width(), 1), dstRow,
-                                rowBytes, fillValue, options.fZeroInitialized);
-                    }
-                }
-                *rowsDecoded = dstHeight;
-            }
-            return result;
+                pixelPtr = SkTAddOffset<void>(pixelPtr, rowBytes);
+            }
+            return SkCodec::kSuccess;
         }
         case SkCodec::kNone_SkScanlineOrder: {
-            SkAutoMalloc storage(srcHeight * rowBytes);
+            const int linesNeeded = subsetHeight - samplingOffsetY;
+            SkAutoMalloc storage(linesNeeded * rowBytes);
             uint8_t* storagePtr = static_cast<uint8_t*>(storage.get());
-            int scanlines = fCodec->getScanlines(storagePtr, srcHeight, rowBytes);
-            storagePtr += Y0 * rowBytes;
-            scanlines -= Y0;
-            int y = 0;
-            while (y < dstHeight && scanlines > 0) {
-                memcpy(dst, storagePtr, rowBytes);
+
+            if (!fCodec->skipScanlines(startY)) {
+                fCodec->fillIncompleteImage(info, pixels, rowBytes, options.fZeroInitialized,
+                        dstHeight, 0);
+                return SkCodec::kIncompleteInput;
+            }
+            int scanlines = fCodec->getScanlines(storagePtr, linesNeeded, rowBytes);
+
+            for (int y = 0; y < dstHeight; y++) {
+                memcpy(pixels, storagePtr, info.minRowBytes());
                 storagePtr += sampleY * rowBytes;
-                dst = SkTAddOffset<void>(dst, rowBytes);
-                scanlines -= sampleY;
-                y++;
-            }
-            if (y < dstHeight) {
+                pixels = SkTAddOffset<void>(pixels, rowBytes);
+            }
+
+            if (scanlines < dstHeight) {
                 // fCodec has already handled filling uninitialized memory.
-                *rowsDecoded = dstHeight;
-                return kIncompleteInput;
-            }
-            return kSuccess;
+                return SkCodec::kIncompleteInput;
+            }
+            return SkCodec::kSuccess;
         }
         default:
             SkASSERT(false);
-            return kUnimplemented;
+            return SkCodec::kUnimplemented;
     }
 }
-
-uint32_t SkScaledCodec::onGetFillValue(SkColorType colorType, SkAlphaType alphaType) const {
-    return fCodec->onGetFillValue(colorType, alphaType);
-}
-
-SkCodec::SkScanlineOrder SkScaledCodec::onGetScanlineOrder() const {
-    return fCodec->onGetScanlineOrder();
-}