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/*
* 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 "SkImageEncoder.h"
#include "SkImageGenerator.h"
#include "SkPixelRef.h"
#include "SkStream.h"
#include "SkStreamPriv.h"
#include "SkTypes.h"
#include "ktx.h"
#include "etc1.h"
///////////////////////////////////////////////////////////////////////////////
// KTX Image Encoder
//
// 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 encoder takes a best guess at how to encode the bitmap passed to it. If
// there is an installed discardable pixel ref with existing PKM data, then we
// will repurpose the existing ETC1 data into a KTX file. If the data contains
// KTX data, then we simply return a copy of the same data. For all other files,
// the underlying KTX library tries to do its best to encode the appropriate
// data specified by the bitmap based on the config. (i.e. kAlpha8_Config will
// be represented as a full resolution 8-bit image dump with the appropriate
// OpenGL defines in the header).
class SkKTXImageEncoder : public SkImageEncoder {
protected:
bool onEncode(SkWStream* stream, const SkBitmap& bm, int quality) override;
private:
virtual bool encodePKM(SkWStream* stream, const SkData *data);
typedef SkImageEncoder INHERITED;
};
bool SkKTXImageEncoder::onEncode(SkWStream* stream, const SkBitmap& bitmap, int) {
if (!bitmap.pixelRef()) {
return false;
}
sk_sp<SkData> data(bitmap.pixelRef()->refEncodedData());
// Is this even encoded data?
if (data) {
const uint8_t *bytes = data->bytes();
if (etc1_pkm_is_valid(bytes)) {
return this->encodePKM(stream, data.get());
}
// Is it a KTX file??
if (SkKTXFile::is_ktx(bytes, data->size())) {
return stream->write(bytes, data->size());
}
// If it's neither a KTX nor a PKM, then we need to
// get at the actual pixels, so fall through and decompress...
}
return SkKTXFile::WriteBitmapToKTX(stream, bitmap);
}
bool SkKTXImageEncoder::encodePKM(SkWStream* stream, const SkData *data) {
const uint8_t* bytes = data->bytes();
SkASSERT(etc1_pkm_is_valid(bytes));
etc1_uint32 width = etc1_pkm_get_width(bytes);
etc1_uint32 height = etc1_pkm_get_height(bytes);
// ETC1 Data is stored as compressed 4x4 pixel blocks, so we must make sure
// that our dimensions are valid.
if (width == 0 || (width & 3) != 0 || height == 0 || (height & 3) != 0) {
return false;
}
// Advance pointer to etc1 data.
bytes += ETC_PKM_HEADER_SIZE;
return SkKTXFile::WriteETC1ToKTX(stream, bytes, width, height);
}
/////////////////////////////////////////////////////////////////////////////////////////
DEFINE_ENCODER_CREATOR(KTXImageEncoder);
/////////////////////////////////////////////////////////////////////////////////////////
SkImageEncoder* sk_libktx_efactory(SkImageEncoder::Type t) {
return (SkImageEncoder::kKTX_Type == t) ? new SkKTXImageEncoder : nullptr;
}
static SkImageEncoder_EncodeReg gEReg(sk_libktx_efactory);
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