Revert of Delete SkImageDecoder

src/images/SkImageDecoder_pkm.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 "SkData.h"
+#include "SkImageDecoder.h"
+#include "SkScaledBitmapSampler.h"
+#include "SkStream.h"
+#include "SkStreamPriv.h"
+#include "SkTextureCompressor.h"
+#include "SkTypes.h"
+
+#include "etc1.h"
+
+class SkPKMImageDecoder : public SkImageDecoder {
+public:
+    SkPKMImageDecoder() { }
+
+    Format getFormat() const override {
+        return kPKM_Format;
+    }
+
+protected:
+    Result onDecode(SkStream* stream, SkBitmap* bm, Mode) override;
+
+private:
+    typedef SkImageDecoder INHERITED;
+};
+
+/////////////////////////////////////////////////////////////////////////////////////////
+
+SkImageDecoder::Result SkPKMImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
+    sk_sp<SkData> data(SkCopyStreamToData(stream));
+    if (!data || !data->size()) {
+        return kFailure;
+    }
+
+    unsigned char* buf = (unsigned char*) data->data();
+
+    // Make sure original PKM header is there...
+    SkASSERT(etc1_pkm_is_valid(buf));
+
+    const unsigned short width = etc1_pkm_get_width(buf);
+    const unsigned short height = etc1_pkm_get_height(buf);
+
+    // Setup the sampler...
+    SkScaledBitmapSampler sampler(width, height, this->getSampleSize());
+
+    // Set the config...
+    bm->setInfo(SkImageInfo::MakeN32(sampler.scaledWidth(), sampler.scaledHeight(),
+                                     kOpaque_SkAlphaType));
+    if (SkImageDecoder::kDecodeBounds_Mode == mode) {
+        return kSuccess;
+    }
+
+    if (!this->allocPixelRef(bm, nullptr)) {
+        return kFailure;
+    }
+
+    // Lock the pixels, since we're about to write to them...
+    SkAutoLockPixels alp(*bm);
+
+    if (!sampler.begin(bm, SkScaledBitmapSampler::kRGB, *this)) {
+        return kFailure;
+    }
+
+    // Advance buffer past the header
+    buf += ETC_PKM_HEADER_SIZE;
+
+    // ETC1 Data is encoded as RGB pixels, so we should extract it as such
+    int nPixels = width * height;
+    SkAutoMalloc outRGBData(nPixels * 3);
+    uint8_t *outRGBDataPtr = reinterpret_cast<uint8_t *>(outRGBData.get());
+
+    // Decode ETC1
+    if (!SkTextureCompressor::DecompressBufferFromFormat(
+            outRGBDataPtr, width*3, buf, width, height, SkTextureCompressor::kETC1_Format)) {
+        return kFailure;
+    }
+
+    // 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 kSuccess;
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////
+DEFINE_DECODER_CREATOR(PKMImageDecoder);
+/////////////////////////////////////////////////////////////////////////////////////////
+
+static bool is_pkm(SkStreamRewindable* stream) {
+    // Read the PKM header and make sure it's valid.
+    unsigned char buf[ETC_PKM_HEADER_SIZE];
+    if (stream->read((void*)buf, ETC_PKM_HEADER_SIZE) != ETC_PKM_HEADER_SIZE) {
+        return false;
+    }
+
+    return SkToBool(etc1_pkm_is_valid(buf));
+}
+
+static SkImageDecoder* sk_libpkm_dfactory(SkStreamRewindable* stream) {
+    if (is_pkm(stream)) {
+        return new SkPKMImageDecoder;
+    }
+    return nullptr;
+}
+
+static SkImageDecoder_DecodeReg gReg(sk_libpkm_dfactory);
+
+static SkImageDecoder::Format get_format_pkm(SkStreamRewindable* stream) {
+    if (is_pkm(stream)) {
+        return SkImageDecoder::kPKM_Format;
+    }
+    return SkImageDecoder::kUnknown_Format;
+}
+
+static SkImageDecoder_FormatReg gFormatReg(get_format_pkm);