Initial KTX encoder

src/images/SkImageDecoder_ktx.cpp

Index: src/images/SkImageDecoder_ktx.cpp
diff --git a/src/images/SkImageDecoder_ktx.cpp b/src/images/SkImageDecoder_ktx.cpp
index bf3445e98514d9734589d9f18ee98f588e1a8088..6ff245954008fed7845d651436157240ddc2870d 100644
--- a/src/images/SkImageDecoder_ktx.cpp
+++ b/src/images/SkImageDecoder_ktx.cpp
@@ -7,6 +7,7 @@
 
 #include "SkColorPriv.h"
 #include "SkImageDecoder.h"
+#include "SkPixelRef.h"
 #include "SkScaledBitmapSampler.h"
 #include "SkStream.h"
 #include "SkStreamHelpers.h"
@@ -73,7 +74,7 @@ bool SkKTXImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
     bm->setConfig(SkBitmap::kARGB_8888_Config,
                   sampler.scaledWidth(), sampler.scaledHeight(),
                   0,
-                  ktxFile.isRGBA8()? kUnpremul_SkAlphaType : kOpaque_SkAlphaType);
+                  ktxFile.isRGBA8()? kPremul_SkAlphaType : kOpaque_SkAlphaType);
     if (SkImageDecoder::kDecodeBounds_Mode == mode) {
         return true;
     }
@@ -135,6 +136,15 @@ bool SkKTXImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
 
     } else if (ktxFile.isRGBA8()) {
 
+        // If we know that the image contains premultiplied alpha, then
+        // don't premultiply it upon decoding.
+        bool setRequireUnpremul = false;
+        const SkString premulKey("KTXPremultipliedAlpha");
+        if (ktxFile.getValueForKey(premulKey) == SkString("True")) {
+            this->setRequireUnpremultipliedColors(true);

[scroggo, 2014/06/09 14:49:45]

This is intended as a setting for the client. If the client actually wanted
unpremultiplied colors, this will incorrectly give them premultiplied colors.

+            setRequireUnpremul = true;
+        }
+
         // Uncompressed RGBA data
         if (!sampler.begin(bm, SkScaledBitmapSampler::kRGBA, *this)) {
             return false;
@@ -150,14 +160,83 @@ bool SkKTXImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
             srcRow += sampler.srcDY() * srcRowBytes;
         }
 
+        // Reset this in case the decoder needs to be used again.
+        if (setRequireUnpremul) {
+            this->setRequireUnpremultipliedColors(false);

[scroggo, 2014/06/09 14:49:45]

Again, if the client wanted unpremultiplied colors, this would change the
behavior for followup calls.

(FWIW, our main client of SkImageDecoder, Android, does not reuse a decoder.)

+        }
+
         return true;
     }
 
     return false;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
+// KTX Image Encoder
+//
+// 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:
+    virtual bool onEncode(SkWStream* stream, const SkBitmap& bm, int quality) SK_OVERRIDE;
+
+private:
+    virtual bool encodePKM(SkWStream* stream, const SkData *data);
+    typedef SkImageEncoder INHERITED;
+};
+
+bool SkKTXImageEncoder::onEncode(SkWStream* stream, const SkBitmap& bitmap, int) {
+    SkAutoDataUnref data(bitmap.pixelRef()->refEncodedData());
+
+    // Is this even encoded data?
+    if (NULL != data) {
+        const uint8_t *bytes = data->bytes();
+        if (etc1_pkm_is_valid(bytes)) {
+            return this->encodePKM(stream, data);
+        }
+
+        // Is it a KTX file??
+        if (SkKTXFile::is_ktx(bytes)) {
+            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_DECODER_CREATOR(KTXImageDecoder);
+DEFINE_ENCODER_CREATOR(KTXImageEncoder);
 /////////////////////////////////////////////////////////////////////////////////////////
 
 static SkImageDecoder* sk_libktx_dfactory(SkStreamRewindable* stream) {
@@ -167,8 +246,6 @@ static SkImageDecoder* sk_libktx_dfactory(SkStreamRewindable* stream) {
     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;
@@ -176,4 +253,10 @@ static SkImageDecoder::Format get_format_ktx(SkStreamRewindable* stream) {
     return SkImageDecoder::kUnknown_Format;
 }
 
+SkImageEncoder* sk_libktx_efactory(SkImageEncoder::Type t) {
+    return (SkImageEncoder::kKTX_Type == t) ? SkNEW(SkKTXImageEncoder) : NULL;
+}
+
+static SkImageDecoder_DecodeReg gReg(sk_libktx_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_ktx);
+static SkImageEncoder_EncodeReg gEReg(sk_libktx_efactory);