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* Copyright 2011 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkScaledBitmapSampler_DEFINED
#define SkScaledBitmapSampler_DEFINED
#include "SkTypes.h"
#include "SkColor.h"
#include "SkImageDecoder.h"
class SkBitmap;
class SkScaledBitmapSampler {
SkScaledBitmapSampler(int origWidth, int origHeight, int cellSize);
int scaledWidth() const { return fScaledWidth; }
int scaledHeight() const { return fScaledHeight; }
int srcY0() const { return fY0; }
int srcDX() const { return fDX; }
int srcDY() const { return fDY; }
enum SrcConfig {
kGray, // 1 byte per pixel
kIndex, // 1 byte per pixel
kRGB, // 3 bytes per pixel
kRGBX, // 4 byes per pixel (ignore 4th)
kRGBA, // 4 bytes per pixel
kRGB_565 // 2 bytes per pixel
struct Options {
bool fDither;
bool fPremultiplyAlpha;
bool fSkipZeros;
explicit Options(const SkImageDecoder &dec)
: fDither(dec.getDitherImage())
, fPremultiplyAlpha(!dec.getRequireUnpremultipliedColors())
, fSkipZeros(dec.getSkipWritingZeroes())
{ }
// Given a dst bitmap (with pixels already allocated) and a src-config,
// prepares iterator to process the src colors and write them into dst.
// Returns false if the request cannot be fulfulled.
bool begin(SkBitmap* dst, SrcConfig sc, const SkImageDecoder& decoder,
const SkPMColor* = NULL);
bool begin(SkBitmap* dst, SrcConfig sc, const Options& opts,
const SkPMColor* = NULL);
// call with row of src pixels, for y = 0...scaledHeight-1.
// returns true if the row had non-opaque alpha in it
bool next(const uint8_t* SK_RESTRICT src);
// Like next(), but specifies the y value of the source row, so the
// rows can come in any order. If the row is not part of the output
// sample, it will be skipped. Only sampleInterlaced OR next should
// be called for one SkScaledBitmapSampler.
bool sampleInterlaced(const uint8_t* SK_RESTRICT src, int srcY);
typedef bool (*RowProc)(void* SK_RESTRICT dstRow,
const uint8_t* SK_RESTRICT src,
int width, int deltaSrc, int y,
const SkPMColor[]);
int fScaledWidth;
int fScaledHeight;
int fX0; // first X coord to sample
int fY0; // first Y coord (scanline) to sample
int fDX; // step between X samples
int fDY; // step between Y samples
#ifdef SK_DEBUG
// Keep track of whether the caller is using next or sampleInterlaced.
// Only one can be used per sampler.
enum SampleMode {
SampleMode fSampleMode;
// setup state
char* fDstRow; // points into bitmap's pixels
size_t fDstRowBytes;
int fCurrY; // used for dithering
int fSrcPixelSize; // 1, 3, 4
RowProc fRowProc;
// optional reference to the src colors if the src is a palette model
const SkPMColor* fCTable;
#ifdef SK_DEBUG
// Helper class allowing a test to have access to fRowProc.
friend class RowProcTester;