Change SkDecodingImageGenerator API

src/images/SkDecodingImageGenerator.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "SkData.h"
 #include "SkDecodingImageGenerator.h"
-#include "SkData.h"
 #include "SkImageDecoder.h"
+#include "SkImageInfo.h"
 #include "SkImageGenerator.h"
 #include "SkImagePriv.h"
 #include "SkStream.h"
-
+#include "SkUtils.h"
 
 namespace {
 /**
  *  Special allocator used by getPixels(). Uses preallocated memory
  *  provided.
  */
 class TargetAllocator : public SkBitmap::Allocator {
 public:
-    TargetAllocator(void* target, size_t rowBytes, const SkImageInfo& info)
+    TargetAllocator(void* target,
+                    size_t rowBytes,
+                    int width,
+                    int height,
+                    SkBitmap::Config config)
         : fTarget(target)
         , fRowBytes(rowBytes)
-        , fInfo(info) { }
+        , fWidth(width)
+        , fHeight(height)
+        , fConfig(config) { }
+
+    bool isReady() { return (fTarget != NULL); }
 
     virtual bool allocPixelRef(SkBitmap* bm, SkColorTable* ct) SK_OVERRIDE {
-        if ((SkImageInfoToBitmapConfig(fInfo) != bm->config())
-            || (bm->width() != fInfo.fWidth)
-            || (bm->height() != fInfo.fHeight)) {
-            return false;
+        if ((NULL == fTarget)
+            || (fConfig != bm->config())
+            || (fWidth != bm->width())
+            || (fHeight != bm->height())
+            || (ct != NULL)) {
+            // Call default allocator.
+            return bm->allocPixels(NULL, ct);
         }
-        bm->setConfig(bm->config(), bm->width(), bm->height(),
-                      fRowBytes, bm->alphaType());
-        bm->setPixels(fTarget, ct);
+        // make sure fRowBytes is correct.
+        bm->setConfig(fConfig, fWidth, fHeight, fRowBytes, bm->alphaType());
+        // TODO(halcanary): verify that all callers of this function
+        // will respect new RowBytes.  Will be moot once rowbytes belongs
+        // to PixelRef.
+        bm->setPixels(fTarget, NULL);
+        fTarget = NULL;  // never alloc same pixels twice!
         return true;
     }
 
 private:
-    void* fTarget;
-    size_t fRowBytes;
-    SkImageInfo fInfo;
+    void* fTarget;  // Block of memory to be supplied as pixel memory
+                    // in allocPixelRef.  Must be large enough to hold
+                    // a bitmap described by fWidth, fHeight, and
+                    // fRowBytes.
+    size_t fRowBytes;  // rowbytes for the destination bitmap
+    int fWidth;   // Along with fHeight and fConfig, the information
+    int fHeight;  // about the bitmap whose pixels this allocator is
+                  // expected to allocate. If they do not match the
+                  // bitmap passed to allocPixelRef, it is assumed
+                  // that the bitmap will be copied to a bitmap with
+                  // the correct info using this allocator, so the
+                  // default allocator will be used instead of
+                  // fTarget.
+    SkBitmap::Config fConfig;
     typedef SkBitmap::Allocator INHERITED;
 };
-}  // namespace
-////////////////////////////////////////////////////////////////////////////////
 
-SkDecodingImageGenerator::SkDecodingImageGenerator(SkData* data)
-    : fData(data)
-    , fHasInfo(false)
-    , fDoCopyTo(false) {
-    SkASSERT(fData != NULL);
-    fStream = SkNEW_ARGS(SkMemoryStream, (fData));
-    SkASSERT(fStream != NULL);
-    SkASSERT(fStream->unique());
-    fData->ref();
-}
+/**
+ *  An implementation of SkImageGenerator that calls into
+ *  SkImageDecoder.  Since the consumers of this class only rely on
+ *  virtual functions, we hide all implementation details inside this
+ *  source file.  This implementaion of getInfo() always returns true.
+ */
+class DecodingImageGenerator : public SkImageGenerator {
+public:
+    DecodingImageGenerator(SkData* data,
+                           SkStreamRewindable* stream,
+                           const SkImageInfo& info,
+                           int sampleSize,
+                           bool ditherImage,
+                           SkBitmap::Config requestedConfig)
+        : fData(data)
+        , fStream(stream)
+        , fInfo(info)
+        , fSampleSize(sampleSize)
+        , fDitherImage(ditherImage)
+        , fRequestedConfig(requestedConfig) {
+        SkASSERT(stream != NULL);
+        SkSafeRef(fData);  // may be NULL.
+    }
+    virtual ~DecodingImageGenerator() {
+        SkSafeUnref(fData);
+        fStream->unref();
+    }
 
-SkDecodingImageGenerator::SkDecodingImageGenerator(SkStreamRewindable* stream)
-    : fData(NULL)
-    , fStream(stream)
-    , fHasInfo(false)
-    , fDoCopyTo(false) {
-    SkASSERT(fStream != NULL);
-    SkASSERT(fStream->unique());
-}
+    virtual SkData* refEncodedData() SK_OVERRIDE;
 
-SkDecodingImageGenerator::~SkDecodingImageGenerator() {
-    SkSafeUnref(fData);
-    fStream->unref();
-}
+    virtual bool getInfo(SkImageInfo* info) SK_OVERRIDE {
+        if (info != NULL) {
+            *info = fInfo;
+        }
+        return true;
+    }
 
-// TODO(halcanary): Give this macro a better name and move it into SkTypes.h
+    virtual bool getPixels(const SkImageInfo& info,
+                           void* pixels,
+                           size_t rowBytes) SK_OVERRIDE;
+
+private:
+    SkData*                fData;
+    SkStreamRewindable*    fStream;
+    const SkImageInfo      fInfo;
+    const int              fSampleSize;
+    const bool             fDitherImage;
+    const SkBitmap::Config fRequestedConfig;
+    typedef SkImageGenerator INHERITED;
+};
+
 #ifdef SK_DEBUG
     #define SkCheckResult(expr, value)  SkASSERT((value) == (expr))
 #else
     #define SkCheckResult(expr, value)  (void)(expr)
 #endif
 
-SkData* SkDecodingImageGenerator::refEncodedData() {
+
+SkData* DecodingImageGenerator::refEncodedData() {
     // This functionality is used in `gm --serialize`
+    // Does not encode options.
     if (fData != NULL) {
         return SkSafeRef(fData);
     }
     // TODO(halcanary): SkStreamRewindable needs a refData() function
     // which returns a cheap copy of the underlying data.
     if (!fStream->rewind()) {
         return NULL;
     }
     size_t length = fStream->getLength();
     if (0 == length) {
         return NULL;
     }
     void* buffer = sk_malloc_flags(length, 0);
     SkCheckResult(fStream->read(buffer, length), length);
     fData = SkData::NewFromMalloc(buffer, length);
     return SkSafeRef(fData);
 }
 
-bool SkDecodingImageGenerator::getInfo(SkImageInfo* info) {
-    // info can be NULL.  If so, will update fInfo, fDoCopyTo, and fHasInfo.
-    if (fHasInfo) {
-        if (info != NULL) {
-            *info = fInfo;
+// TODO(halcanary) move this function into a standard header.
+static bool config_to_colorType(SkBitmap::Config config, SkColorType* ctOut) {
+    SkColorType ct;
+    switch (config) {
+        case SkBitmap::kA8_Config:
+            ct = kAlpha_8_SkColorType;
+            break;
+        case SkBitmap::kIndex8_Config:
+            ct = kIndex_8_SkColorType;
+            break;
+        case SkBitmap::kRGB_565_Config:
+            ct = kRGB_565_SkColorType;
+            break;
+        case SkBitmap::kARGB_4444_Config:
+            ct = kARGB_4444_SkColorType;
+            break;
+        case SkBitmap::kARGB_8888_Config:
+            ct = kPMColor_SkColorType;
+            break;
+        case SkBitmap::kNo_Config:
+        default:
+            return false;
+    }
+    if (ctOut) {
+        *ctOut = ct;
+    }
+    return true;
+}
+
+// A contructor-type function that returns NULL on failure.  This
+// prevents the returned SkImageGenerator from ever being in a bad
+// state.
+static SkImageGenerator* create_decoding_generator(SkData* data,
+                                                   SkStreamRewindable* stream,
+                                                   const SkDecoderOptions& opts) {
+    SkASSERT(stream);
+    SkAutoTUnref<SkStreamRewindable> autoStream(stream);  // always unref this.
+    if (SkBitmap::kIndex8_Config == opts.fRequestedConfig) {
+        // We do not support indexed color with SkImageGenerators,
+        return NULL;
+    }
+    SkAssertResult(autoStream->rewind());
+    SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(autoStream));
+    if (NULL == decoder.get()) {
+        return NULL;
+    }
+    SkBitmap bitmap;
+    decoder->setSampleSize(opts.fSampleSize);
+    if (!decoder->decode(stream, &bitmap,
+                         SkImageDecoder::kDecodeBounds_Mode)) {
+        return NULL;
+    }
+    if (bitmap.config() == SkBitmap::kNo_Config) {
+        return NULL;
+    }
+
+    SkImageInfo info;
+    SkBitmap::Config config = opts.fRequestedConfig;
+    if (opts.fRequestedConfig == SkBitmap::kNo_Config) {
+        // Use default config.
+        if (SkBitmap::kIndex8_Config == bitmap.config()) {
+            // We don't support kIndex8 because we don't support
+            // colortables in this workflow.
+            config = SkBitmap::kARGB_8888_Config;
+            info.fWidth = bitmap.width();
+            info.fHeight = bitmap.height();
+            info.fColorType = kPMColor_SkColorType;
+            info.fAlphaType = bitmap.alphaType();
+        } else {
+            config = bitmap.config();  // Save for later!
+            if (!bitmap.asImageInfo(&info)) {
+                SkDEBUGFAIL("Getting SkImageInfo from bitmap failed.");
+                return NULL;
+            }
         }
-        return true;
+    } else {
+        if (!bitmap.canCopyTo(opts.fRequestedConfig)) {
+            SkASSERT(bitmap.config() != opts.fRequestedConfig);
+            return NULL;  // Can not translate to needed config.
+        }
+        info.fWidth = bitmap.width();
+        info.fHeight = bitmap.height();
+        if (!config_to_colorType(opts.fRequestedConfig,
+                                 &(info.fColorType))) {
+            SkDEBUGFAIL("SkBitmapConfigToColorType fails.");
+            return NULL;
+        }
+        info.fAlphaType = bitmap.alphaType();
     }
+    return SkNEW_ARGS(DecodingImageGenerator,
+                      (data, autoStream.detach(), info,
+                       opts.fSampleSize, opts.fDitherImage, config));
+}
+
+#ifdef SK_DEBUG
+inline bool check_alpha(SkAlphaType reported, SkAlphaType actual) {
+    return ((reported == actual)
+            || ((reported == kPremul_SkAlphaType)
+                && (actual == kOpaque_SkAlphaType)));
+}
+#endif  // SK_DEBUG
+
+bool DecodingImageGenerator::getPixels(const SkImageInfo& info,
+                                       void* pixels,
+                                       size_t rowBytes) {
+    if (NULL == pixels) {
+        return false;
+    }
+    if (fInfo != info) {
+        // The caller has specified a different info.  This is an
+        // error for this kind of SkImageGenerator.  Use the Options
+        // to change the settings.
+        return false;
+    }
+    int bpp = SkBitmap::ComputeBytesPerPixel(fRequestedConfig);
+    if (static_cast<size_t>(bpp * info.fWidth) > rowBytes) {
+        // The caller has specified a bad rowBytes.
+        return false;
+    }
+
     SkAssertResult(fStream->rewind());
     SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(fStream));
     if (NULL == decoder.get()) {
         return false;
     }
+    decoder->setDitherImage(fDitherImage);
+    decoder->setSampleSize(fSampleSize);
+
     SkBitmap bitmap;
-    if (!decoder->decode(fStream, &bitmap,
-                         SkImageDecoder::kDecodeBounds_Mode)) {
-        return false;
-    }
-    if (bitmap.config() == SkBitmap::kNo_Config) {
-        return false;
-    }
-    if (!bitmap.asImageInfo(&fInfo)) {
-        // We can't use bitmap.config() as is.
-        if (!bitmap.canCopyTo(SkBitmap::kARGB_8888_Config)) {
-            SkDEBUGFAIL("!bitmap->canCopyTo(SkBitmap::kARGB_8888_Config)");
-            return false;
-        }
-        fDoCopyTo = true;
-        fInfo.fWidth = bitmap.width();
-        fInfo.fHeight = bitmap.height();
-        fInfo.fColorType = kPMColor_SkColorType;
-        fInfo.fAlphaType = bitmap.alphaType();
-    }
-    if (info != NULL) {
-        *info = fInfo;
-    }
-    fHasInfo = true;
-    return true;
-}
-
-bool SkDecodingImageGenerator::getPixels(const SkImageInfo& info,
-                                         void* pixels,
-                                         size_t rowBytes) {
-    if (NULL == pixels) {
-        return false;
-    }
-    if (!this->getInfo(NULL)) {
-        return false;
-    }
-    if (SkImageInfoToBitmapConfig(info) == SkBitmap::kNo_Config) {
-        return false;  // Unsupported SkColorType.
-    }
-    SkAssertResult(fStream->rewind());
-    SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(fStream));
-    if (NULL == decoder.get()) {
-        return false;
-    }
-    if (fInfo != info) {
-        // The caller has specified a different info.  For now, this
-        // is an error.  In the future, we will check to see if we can
-        // convert.
-        return false;
-    }
-    int bpp = SkBitmap::ComputeBytesPerPixel(SkImageInfoToBitmapConfig(info));
-    if (static_cast<size_t>(bpp * info.fWidth) > rowBytes) {
-        return false;
-    }
-    SkBitmap bitmap;
-    if (!bitmap.setConfig(info, rowBytes)) {
-        return false;
-    }
-
-    TargetAllocator allocator(pixels, rowBytes, info);
-    if (!fDoCopyTo) {
-        decoder->setAllocator(&allocator);
-    }
-    bool success = decoder->decode(fStream, &bitmap,
+    TargetAllocator allocator(pixels, rowBytes, info.fWidth,
+                              info.fHeight, fRequestedConfig);
+    decoder->setAllocator(&allocator);
+    bool success = decoder->decode(fStream, &bitmap, fRequestedConfig,
                                    SkImageDecoder::kDecodePixels_Mode);
     decoder->setAllocator(NULL);
     if (!success) {
         return false;
     }
-    if (fDoCopyTo) {
-        SkBitmap bm8888;
-        bitmap.copyTo(&bm8888, SkBitmap::kARGB_8888_Config, &allocator);
+    if (allocator.isReady()) {  // Did not use pixels!
+        SkBitmap bm;
+        SkASSERT(bitmap.canCopyTo(fRequestedConfig));
+        if (!bitmap.copyTo(&bm, fRequestedConfig, &allocator)
+            || allocator.isReady()) {
+            SkDEBUGFAIL("bitmap.copyTo(requestedConfig) failed.");
+            // Earlier we checked canCopyto(); we expect consistency.
+            return false;
+        }
+        SkASSERT(check_alpha(fInfo.fAlphaType, bm.alphaType()));
+    } else {
+        SkASSERT(check_alpha(fInfo.fAlphaType, bitmap.alphaType()));
     }
     return true;
 }
-bool SkDecodingImageGenerator::Install(SkData* data, SkBitmap* dst,
-                                       SkDiscardableMemory::Factory* factory) {
+}  // namespace
+////////////////////////////////////////////////////////////////////////////////
+
+SkImageGenerator* SkNewDecodingImageGenerator(SkData* data,
+                                              const SkDecoderOptions& opts) {
     SkASSERT(data != NULL);
-    SkASSERT(dst != NULL);
-    SkImageGenerator* gen(SkNEW_ARGS(SkDecodingImageGenerator, (data)));
-    return SkInstallDiscardablePixelRef(gen, dst, factory);
+    if (NULL == data) {
+        return NULL;
+    }
+    SkStreamRewindable* stream = SkNEW_ARGS(SkMemoryStream, (data));
+    SkASSERT(stream != NULL);
+    SkASSERT(stream->unique());
+    return create_decoding_generator(data, stream, opts);
 }
 
-bool SkDecodingImageGenerator::Install(SkStreamRewindable* stream,
-                                       SkBitmap* dst,
-                                       SkDiscardableMemory::Factory* factory) {
+SkImageGenerator* SkNewDecodingImageGenerator(SkStreamRewindable* stream,
+                                              const SkDecoderOptions& opts) {
     SkASSERT(stream != NULL);
-    SkASSERT(dst != NULL);
+    SkASSERT(stream->unique());
     if ((stream == NULL) || !stream->unique()) {
         SkSafeUnref(stream);
-        return false;
+        return NULL;
     }
-    SkImageGenerator* gen(SkNEW_ARGS(SkDecodingImageGenerator, (stream)));
-    return SkInstallDiscardablePixelRef(gen, dst, factory);
+    return create_decoding_generator(NULL, stream, opts);
 }
+