src/codec/SkScaledCodec.cpp - platform/external/skia - Gitiles

 /*
  * 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 "SkCodecPriv.h"
 #include "SkScaledCodec.h"
 #include "SkStream.h"
 #include "SkWebpCodec.h"


 SkCodec* SkScaledCodec::NewFromStream(SkStream* stream) {
     bool isWebp = SkWebpCodec::IsWebp(stream);
     if (!stream->rewind()) {
         return nullptr;
     }
     if (isWebp) {
         // Webp codec supports scaling and subsetting natively
         return SkWebpCodec::NewFromStream(stream);
     }

     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream));
     if (nullptr == codec) {
         return nullptr;
     }

     // wrap in new SkScaledCodec
     return new SkScaledCodec(codec.detach());
 }

 SkCodec* SkScaledCodec::NewFromData(SkData* data) {
     if (!data) {
         return nullptr;
     }
     return NewFromStream(new SkMemoryStream(data));
 }

 SkScaledCodec::SkScaledCodec(SkCodec* codec)
     : INHERITED(codec->getInfo(), nullptr)
     , 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;

     // 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;
 }

 /*
  * 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);
 }

 // 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) {

     if (options.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
     }

     if (fCodec->dimensionsSupported(requestedInfo.dimensions())) {
         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) {
         return result;
     }

     SkSampler* sampler = fCodec->getSampler();
     if (!sampler) {
         return kUnimplemented;
     }

     if (sampler->setSampleX(sampleX) != requestedInfo.width()) {
         return kInvalidScale;
     }

     switch(fCodec->getScanlineOrder()) {
         case SkCodec::kTopDown_SkScanlineOrder: {
             result = fCodec->skipScanlines(Y0);
             if (kSuccess != result && kIncompleteInput != result) {
                 return result;
             }
             for (int y = 0; y < dstHeight; y++) {
                 result = fCodec->getScanlines(dst, 1, rowBytes);
                 if (kSuccess != result && kIncompleteInput != result) {
                     return result;
                 }
                 if (y < dstHeight - 1) {
                     result = fCodec->skipScanlines(sampleY - 1);
                     if (kSuccess != result && kIncompleteInput != result) {
                         return result;
                     }
                 }
                 dst = SkTAddOffset<void>(dst, rowBytes);
             }
             return result;
         }
         case SkCodec::kBottomUp_SkScanlineOrder:
         case SkCodec::kOutOfOrder_SkScanlineOrder: {
             for (int 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));
                     result = fCodec->getScanlines(dstPtr, 1, rowBytes);
                     if (kSuccess != result && kIncompleteInput != result) {
                         return result;
                     }
                 } else {
                     result = fCodec->skipScanlines(1);
                     if (kSuccess != result && kIncompleteInput != result) {
                         return result;
                     }
                 }
             }
             return result;
         }
         case SkCodec::kNone_SkScanlineOrder: {
             SkAutoMalloc storage(srcHeight * rowBytes);
             uint8_t* storagePtr = static_cast<uint8_t*>(storage.get());
             result = fCodec->getScanlines(storagePtr, srcHeight, rowBytes);
             if (kSuccess != result && kIncompleteInput != result) {
                 return result;
             }
             storagePtr += Y0 * rowBytes;
             for (int y = 0; y < dstHeight; y++) {
                 memcpy(dst, storagePtr, rowBytes);
                 storagePtr += sampleY * rowBytes;
                 dst = SkTAddOffset<void>(dst, rowBytes);
             }
             return result;
         }
         default:
             SkASSERT(false);
             return kUnimplemented;
     }
 }
	/*
	* 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 "SkCodecPriv.h"
	#include "SkScaledCodec.h"
	#include "SkStream.h"
	#include "SkWebpCodec.h"


	SkCodec* SkScaledCodec::NewFromStream(SkStream* stream) {
	bool isWebp = SkWebpCodec::IsWebp(stream);
	if (!stream->rewind()) {
	return nullptr;
	}
	if (isWebp) {
	// Webp codec supports scaling and subsetting natively
	return SkWebpCodec::NewFromStream(stream);
	}

	SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream));
	if (nullptr == codec) {
	return nullptr;
	}

	// wrap in new SkScaledCodec
	return new SkScaledCodec(codec.detach());
	}

	SkCodec* SkScaledCodec::NewFromData(SkData* data) {
	if (!data) {
	return nullptr;
	}
	return NewFromStream(new SkMemoryStream(data));
	}

	SkScaledCodec::SkScaledCodec(SkCodec* codec)
	: INHERITED(codec->getInfo(), nullptr)
	, 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;

	// 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;
	}

	/*
	* 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);
	}

	// 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) {

	if (options.fSubset) {
	// Subsets are not supported.
	return kUnimplemented;
	}

	if (fCodec->dimensionsSupported(requestedInfo.dimensions())) {
	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) {
	return result;
	}

	SkSampler* sampler = fCodec->getSampler();
	if (!sampler) {
	return kUnimplemented;
	}

	if (sampler->setSampleX(sampleX) != requestedInfo.width()) {
	return kInvalidScale;
	}

	switch(fCodec->getScanlineOrder()) {
	case SkCodec::kTopDown_SkScanlineOrder: {
	result = fCodec->skipScanlines(Y0);
	if (kSuccess != result && kIncompleteInput != result) {
	return result;
	}
	for (int y = 0; y < dstHeight; y++) {
	result = fCodec->getScanlines(dst, 1, rowBytes);
	if (kSuccess != result && kIncompleteInput != result) {
	return result;
	}
	if (y < dstHeight - 1) {
	result = fCodec->skipScanlines(sampleY - 1);
	if (kSuccess != result && kIncompleteInput != result) {
	return result;
	}
	}
	dst = SkTAddOffset<void>(dst, rowBytes);
	}
	return result;
	}
	case SkCodec::kBottomUp_SkScanlineOrder:
	case SkCodec::kOutOfOrder_SkScanlineOrder: {
	for (int 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));
	result = fCodec->getScanlines(dstPtr, 1, rowBytes);
	if (kSuccess != result && kIncompleteInput != result) {
	return result;
	}
	} else {
	result = fCodec->skipScanlines(1);
	if (kSuccess != result && kIncompleteInput != result) {
	return result;
	}
	}
	}
	return result;
	}
	case SkCodec::kNone_SkScanlineOrder: {
	SkAutoMalloc storage(srcHeight * rowBytes);
	uint8_t* storagePtr = static_cast<uint8_t*>(storage.get());
	result = fCodec->getScanlines(storagePtr, srcHeight, rowBytes);
	if (kSuccess != result && kIncompleteInput != result) {
	return result;
	}
	storagePtr += Y0 * rowBytes;
	for (int y = 0; y < dstHeight; y++) {
	memcpy(dst, storagePtr, rowBytes);
	storagePtr += sampleY * rowBytes;
	dst = SkTAddOffset<void>(dst, rowBytes);
	}
	return result;
	}
	default:
	SkASSERT(false);
	return kUnimplemented;
	}
	}