Disable png encodes from Alpha8, Float16

src/images/SkPNGImageEncoder.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageEncoder.h"
 #include "SkColor.h"
 #include "SkColorPriv.h"
@@ skipping 164 matching lines @@
 private:
     bool doEncode(SkWStream* stream, const SkBitmap& bm,
                   SkAlphaType alphaType, int colorType,
                   int bitDepth, SkColorType ct,
                   png_color_8& sig_bit);
 
     typedef SkImageEncoder INHERITED;
 };
 
 bool SkPNGImageEncoder::onEncode(SkWStream* stream,
-                                 const SkBitmap& originalBitmap,
+                                 const SkBitmap& bitmap,
                                  int /*quality*/) {
-    SkBitmap copy;
-    const SkBitmap* bitmap = &originalBitmap;
-    switch (originalBitmap.colorType()) {
+    SkColorType ct = bitmap.colorType();

[scroggo, 2016/09/12 18:23:00]

nit: Could be const?

+    switch (ct) {
         case kIndex_8_SkColorType:
         case kGray_8_SkColorType:
         case kRGBA_8888_SkColorType:
         case kBGRA_8888_SkColorType:
         case kARGB_4444_SkColorType:
         case kRGB_565_SkColorType:
             break;
         default:
-            // TODO(scroggo): support Alpha_8 as Grayscale(black)+Alpha
-            if (originalBitmap.copyTo(&copy, kN32_SkColorType)) {
-                bitmap = ©
-            }
+            return false;
     }
-    SkColorType ct = bitmap->colorType();
 
-    SkAlphaType alphaType = bitmap->alphaType();
+    SkAlphaType alphaType = bitmap.alphaType();
     switch (alphaType) {
         case kUnpremul_SkAlphaType:
             if (kARGB_4444_SkColorType == ct) {
                 return false;
             }
 
             break;
         case kOpaque_SkAlphaType:
         case kPremul_SkAlphaType:
             break;
@@ skipping 39 matching lines @@
             sig_bit.red = 5;
             sig_bit.green = 6;
             sig_bit.blue = 5;
             colorType = PNG_COLOR_TYPE_RGB;
             SkASSERT(isOpaque);
             break;
         default:
             return false;
     }
 
-    SkAutoLockPixels alp(*bitmap);
+    SkAutoLockPixels alp(bitmap);
     // readyToDraw checks for pixels (and colortable if that is required)
-    if (!bitmap->readyToDraw()) {
+    if (!bitmap.readyToDraw()) {
         return false;
     }
 
     // we must do this after we have locked the pixels
-    SkColorTable* ctable = bitmap->getColorTable();
+    SkColorTable* ctable = bitmap.getColorTable();
     if (ctable) {
         if (ctable->count() == 0) {
             return false;
         }
         // check if we can store in fewer than 8 bits
         bitDepth = computeBitDepth(ctable->count());
     }
 
-    return doEncode(stream, *bitmap, alphaType, colorType, bitDepth, ct, sig_bit);
+    return doEncode(stream, bitmap, alphaType, colorType, bitDepth, ct, sig_bit);
 }
 
 bool SkPNGImageEncoder::doEncode(SkWStream* stream, const SkBitmap& bitmap,
                   SkAlphaType alphaType, int colorType,
                   int bitDepth, SkColorType ct,
                   png_color_8& sig_bit) {
 
     png_structp png_ptr;
     png_infop info_ptr;
 
@@ skipping 69 matching lines @@
 
 ///////////////////////////////////////////////////////////////////////////////
 DEFINE_ENCODER_CREATOR(PNGImageEncoder);
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? new SkPNGImageEncoder : nullptr;
 }
 
 static SkImageEncoder_EncodeReg gEReg(sk_libpng_efactory);