Initial KTX file decoder

src/images/SkImageDecoder_ktx.cpp

+/*
+ * 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 "SkColorPriv.h"
+#include "SkImageDecoder.h"
+#include "SkScaledBitmapSampler.h"
+#include "SkStream.h"
+#include "SkStreamHelpers.h"
+#include "SkTypes.h"
+
+#include "ktx.h"
+#include "etc1.h"
+
+/////////////////////////////////////////////////////////////////////////////////////////
+
+
+/////////////////////////////////////////////////////////////////////////////////////////
+
+// KTX Image decoder
+// ---
+// KTX is a general texture data storage file format ratified by the Khronos Group. As an
+// overview, a KTX file contains all of the appropriate values needed to fully specify a
+// texture in an OpenGL application, including the use of compressed data.
+//
+// This decoder is meant to be used with an SkDiscardablePixelRef so that GPU backends
+// can sniff the data before creating a texture. If they encounter a compressed format
+// that they understand, they can then upload the data directly to the GPU. Otherwise,
+// they will decode the data into a format that Skia supports.
+
+class SkKTXImageDecoder : public SkImageDecoder {
+public:
+    SkKTXImageDecoder() { }
+
+    virtual Format getFormat() const SK_OVERRIDE {
+        return kKTX_Format;
+    }
+
+protected:
+    virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode) SK_OVERRIDE;
+
+private:
+    typedef SkImageDecoder INHERITED;
+};
+
+bool SkKTXImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
+    // TODO: Implement SkStream::copyToData() that's cheap for memory and file streams
+    SkAutoDataUnref data(CopyStreamToData(stream));
+    if (NULL == data) {
+        return false;
+    }
+
+    SkKTXFile ktxFile(data);
+    if (!ktxFile.valid()) {
+        return false;
+    }
+
+    const unsigned short width = ktxFile.width();
+    const unsigned short height = ktxFile.height();
+
+    // should we allow the Chooser (if present) to pick a config for us???
+    if (!this->chooseFromOneChoice(SkBitmap::kARGB_8888_Config, width, height)) {
+        return false;
+    }
+
+    // Setup the sampler...
+    SkScaledBitmapSampler sampler(width, height, this->getSampleSize());
+
+    // Set the config...
+    bm->setConfig(SkBitmap::kARGB_8888_Config,
+                  sampler.scaledWidth(), sampler.scaledHeight(),
+                  0,
+                  ktxFile.isRGBA8()? kUnpremul_SkAlphaType : kOpaque_SkAlphaType);
+    if (SkImageDecoder::kDecodeBounds_Mode == mode) {
+        return true;
+    }
+    
+    // If we've made it this far, then we know how to grok the data.
+    if (!this->allocPixelRef(bm, NULL)) {
+        return false;
+    }
+
+    // Lock the pixels, since we're about to write to them...
+    SkAutoLockPixels alp(*bm);
+
+    if (ktxFile.isETC1()) {
+        if (!sampler.begin(bm, SkScaledBitmapSampler::kRGB, *this)) {
+            return false;
+        }
+
+        // ETC1 Data is encoded as RGB pixels, so we should extract it as such
+        int nPixels = width * height;
+        SkAutoMalloc outRGBData(nPixels * 3);
+        etc1_byte *outRGBDataPtr = reinterpret_cast<etc1_byte *>(outRGBData.get());
+
+        // Decode ETC1
+        const etc1_byte *buf = reinterpret_cast<const etc1_byte *>(ktxFile.pixelData());
+        if (etc1_decode_image(buf, outRGBDataPtr, width, height, 3, width*3)) {
+            return false;
+        }
+
+        // Set each of the pixels...
+        const int srcRowBytes = width * 3;
+        const int dstHeight = sampler.scaledHeight();
+        const uint8_t *srcRow = reinterpret_cast<uint8_t *>(outRGBDataPtr);
+        srcRow += sampler.srcY0() * srcRowBytes;
+        for (int y = 0; y < dstHeight; ++y) {
+            sampler.next(srcRow);
+            srcRow += sampler.srcDY() * srcRowBytes;
+        }
+
+        return true;
+
+    } else if (ktxFile.isRGB8()) {
+
+        // Uncompressed RGB data (without alpha)
+        if (!sampler.begin(bm, SkScaledBitmapSampler::kRGB, *this)) {
+            return false;
+        }
+
+        // Just need to read RGB pixels
+        const int srcRowBytes = width * 3;
+        const int dstHeight = sampler.scaledHeight();
+        const uint8_t *srcRow = reinterpret_cast<const uint8_t *>(ktxFile.pixelData());
+        srcRow += sampler.srcY0() * srcRowBytes;
+        for (int y = 0; y < dstHeight; ++y) {
+            sampler.next(srcRow);
+            srcRow += sampler.srcDY() * srcRowBytes;
+        }
+
+        return true;
+
+    } else if (ktxFile.isRGBA8()) {
+
+        // Uncompressed RGBA data
+        if (!sampler.begin(bm, SkScaledBitmapSampler::kRGBA, *this)) {
+            return false;
+        }
+
+        // Just need to read RGBA pixels
+        const int srcRowBytes = width * 4;
+        const int dstHeight = sampler.scaledHeight();
+        const uint8_t *srcRow = reinterpret_cast<const uint8_t *>(ktxFile.pixelData());
+        srcRow += sampler.srcY0() * srcRowBytes;
+        for (int y = 0; y < dstHeight; ++y) {
+            sampler.next(srcRow);
+            srcRow += sampler.srcDY() * srcRowBytes;
+        }
+
+        return true;
+    }
+
+    return false;
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////
+DEFINE_DECODER_CREATOR(KTXImageDecoder);
+/////////////////////////////////////////////////////////////////////////////////////////
+
+static SkImageDecoder* sk_libktx_dfactory(SkStreamRewindable* stream) {
+    if (SkKTXFile::is_ktx(stream)) {
+        return SkNEW(SkKTXImageDecoder);
+    }
+    return NULL;
+}
+
+static SkImageDecoder_DecodeReg gReg(sk_libktx_dfactory);
+
+static SkImageDecoder::Format get_format_ktx(SkStreamRewindable* stream) {
+    if (SkKTXFile::is_ktx(stream)) {
+        return SkImageDecoder::kKTX_Format;
+    }
+    return SkImageDecoder::kUnknown_Format;
+}
+
+static SkImageDecoder_FormatReg gFormatReg(get_format_ktx);