- Add astcbitmap to gm slides

src/images/SkImageDecoder_astc.cpp

Index: src/images/SkImageDecoder_astc.cpp
diff --git a/src/images/SkImageDecoder_astc.cpp b/src/images/SkImageDecoder_astc.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..79e98047d6b214c59db963c7d26aa25253295a3e
--- /dev/null
+++ b/src/images/SkImageDecoder_astc.cpp
@@ -0,0 +1,209 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkEndian.h"
+#include "SkColorPriv.h"
+#include "SkImageDecoder.h"
+#include "SkScaledBitmapSampler.h"
+#include "SkStream.h"
+#include "SkStreamPriv.h"
+#include "SkTypes.h"
+
+#include "SkTextureCompressor.h"
+
+class SkASTCImageDecoder : public SkImageDecoder {
+public:
+    SkASTCImageDecoder() { }
+
+    virtual Format getFormat() const SK_OVERRIDE {
+        return kASTC_Format;
+    }
+
+protected:
+    virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode) SK_OVERRIDE;
+
+private:
+    typedef SkImageDecoder INHERITED;
+};
+
+/////////////////////////////////////////////////////////////////////////////////////////
+
+static const uint32_t kASTCMagicNumber = 0x5CA1AB13;
+
+static inline int read_24bit(const uint8_t* buf) {
+    // Assume everything is little endian...
+    return
+        static_cast<int>(buf[0]) |
+        (static_cast<int>(buf[1]) << 8) |
+        (static_cast<int>(buf[2]) << 16);
+}
+
+bool SkASTCImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
+    SkAutoMalloc autoMal;
+    const size_t length = SkCopyStreamToStorage(&autoMal, stream);
+    if (0 == length) {
+        return false;
+    }
+
+    unsigned char* buf = (unsigned char*)autoMal.get();
+
+    // Make sure that the magic header is there...
+    SkASSERT(SkEndian_SwapLE32(*(reinterpret_cast<uint32_t*>(buf))) == kASTCMagicNumber);
+
+    // Advance past the magic header
+    buf += 4;
+
+    const int blockDimX = buf[0];
+    const int blockDimY = buf[1];
+    const int blockDimZ = buf[2];
+
+    if (1 != blockDimZ) {
+        // We don't support decoding 3D
+        return false;
+    }
+
+    // Choose the proper ASTC format
+    SkTextureCompressor::Format astcFormat;
+    if (4 == blockDimX && 4 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_4x4_Format;
+    } else if (5 == blockDimX && 4 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_5x4_Format;
+    } else if (5 == blockDimX && 5 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_5x5_Format;
+    } else if (6 == blockDimX && 5 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_6x5_Format;
+    } else if (6 == blockDimX && 6 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_6x6_Format;
+    } else if (8 == blockDimX && 5 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_8x5_Format;
+    } else if (8 == blockDimX && 6 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_8x6_Format;
+    } else if (8 == blockDimX && 8 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_8x8_Format;
+    } else if (10 == blockDimX && 5 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_10x5_Format;
+    } else if (10 == blockDimX && 6 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_10x6_Format;
+    } else if (10 == blockDimX && 8 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_10x8_Format;
+    } else if (10 == blockDimX && 10 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_10x10_Format;
+    } else if (12 == blockDimX && 10 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_12x10_Format;
+    } else if (12 == blockDimX && 12 == blockDimY) {
+        astcFormat = SkTextureCompressor::kASTC_12x12_Format;
+    } else {
+        // We don't support any other block dimensions..
+        return false;
+    }
+
+    // Advance buf past the block dimensions
+    buf += 3;
+
+    // Read the width/height/depth from the buffer...
+    const int width = read_24bit(buf);
+    const int height = read_24bit(buf + 3);
+    const int depth = read_24bit(buf + 6);
+
+    if (1 != depth) {
+        // We don't support decoding 3D.
+        return false;
+    }
+
+    // Advance the buffer past the image dimensions
+    buf += 9;
+
+#ifdef SK_SUPPORT_LEGACY_IMAGEDECODER_CHOOSER
+    // should we allow the Chooser (if present) to pick a config for us???
+    if (!this->chooseFromOneChoice(kN32_SkColorType, width, height)) {
+        return false;
+    }
+#endif
+
+    // Setup the sampler...
+    SkScaledBitmapSampler sampler(width, height, this->getSampleSize());
+
+    // Determine the alpha of the bitmap...
+    SkAlphaType alphaType = kOpaque_SkAlphaType;
+    if (this->getRequireUnpremultipliedColors()) {
+        alphaType = kUnpremul_SkAlphaType;
+    } else {
+        alphaType = kPremul_SkAlphaType;
+    }
+
+    // Set the config...
+    bm->setInfo(SkImageInfo::MakeN32(sampler.scaledWidth(), sampler.scaledHeight(), alphaType));
+
+    if (SkImageDecoder::kDecodeBounds_Mode == mode) {
+        return true;
+    }
+
+    if (!this->allocPixelRef(bm, NULL)) {
+        return false;
+    }
+
+    // Lock the pixels, since we're about to write to them...
+    SkAutoLockPixels alp(*bm);
+
+    if (!sampler.begin(bm, SkScaledBitmapSampler::kRGBA, *this)) {
+        return false;
+    }
+
+    // ASTC Data is encoded as RGBA pixels, so we should extract it as such
+    int nPixels = width * height;
+    SkAutoMalloc outRGBAData(nPixels * 4);
+    uint8_t *outRGBADataPtr = reinterpret_cast<uint8_t *>(outRGBAData.get());
+
+    // Decode ASTC
+    if (!SkTextureCompressor::DecompressBufferFromFormat(

[scroggo, 2014/10/17 15:31:38]

Due to the way this statement was written to get around length limits, it almost
looks logical, but looking closer, it says:

if (!f()) {
    // do nothing different from if f() returned true
}

What is the intent here? Do we want to behave differently if f() returned false?
Return false from onDecode? Or should we remove the if?

[robertphillips, 2014/10/17 15:41:22]

Ha ha. Given the semantics and the other uses I believe this is missing a
"return false;"

[pavelk, 2014/10/19 20:09:41]

Yes, it most certainly is!

+            outRGBADataPtr, width*4, buf, width, height, astcFormat)) {
+    }
+
+    // Set each of the pixels...
+    const int srcRowBytes = width * 4;
+    const int dstHeight = sampler.scaledHeight();
+    const uint8_t *srcRow = reinterpret_cast<uint8_t *>(outRGBADataPtr);
+    srcRow += sampler.srcY0() * srcRowBytes;
+    for (int y = 0; y < dstHeight; ++y) {
+        sampler.next(srcRow);
+        srcRow += sampler.srcDY() * srcRowBytes;
+    }
+
+    return true;
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////
+DEFINE_DECODER_CREATOR(ASTCImageDecoder);
+/////////////////////////////////////////////////////////////////////////////////////////
+
+static bool is_astc(SkStreamRewindable* stream) {
+    // Read the ASTC header and make sure it's valid.
+    uint32_t magic;
+    if (stream->read((void*)&magic, 4) != 4) {
+        return false;
+    }
+
+    return kASTCMagicNumber == SkEndian_SwapLE32(magic);
+}
+
+static SkImageDecoder* sk_libastc_dfactory(SkStreamRewindable* stream) {
+    if (is_astc(stream)) {
+        return SkNEW(SkASTCImageDecoder);
+    }
+    return NULL;
+}
+
+static SkImageDecoder_DecodeReg gReg(sk_libastc_dfactory);
+
+static SkImageDecoder::Format get_format_astc(SkStreamRewindable* stream) {
+    if (is_astc(stream)) {
+        return SkImageDecoder::kASTC_Format;
+    }
+    return SkImageDecoder::kUnknown_Format;
+}
+
+static SkImageDecoder_FormatReg gFormatReg(get_format_astc);