1 /* 2 * Copyright 2017 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkJpegEncoder_DEFINED 9 #define SkJpegEncoder_DEFINED 10 11 #include "SkEncoder.h" 12 13 class SkJpegEncoderMgr; 14 class SkWStream; 15 16 class SK_API SkJpegEncoder : public SkEncoder { 17 public: 18 19 enum class AlphaOption { 20 kIgnore, 21 kBlendOnBlack, 22 }; 23 24 enum class Downsample { 25 /** 26 * Reduction by a factor of two in both the horizontal and vertical directions. 27 */ 28 k420, 29 30 /** 31 * Reduction by a factor of two in the horizontal direction. 32 */ 33 k422, 34 35 /** 36 * No downsampling. 37 */ 38 k444, 39 }; 40 41 struct Options { 42 /** 43 * |fQuality| must be in [0, 100] where 0 corresponds to the lowest quality. 44 */ 45 int fQuality = 100; 46 47 /** 48 * Choose the downsampling factor for the U and V components. This is only 49 * meaningful if the |src| is not kGray, since kGray will not be encoded as YUV. 50 * 51 * Our default value matches the libjpeg-turbo default. 52 */ 53 Downsample fDownsample = Downsample::k420; 54 55 /** 56 * Jpegs must be opaque. This instructs the encoder on how to handle input 57 * images with alpha. 58 * 59 * The default is to ignore the alpha channel and treat the image as opaque. 60 * Another option is to blend the pixels onto a black background before encoding. 61 * In the second case, the encoder supports linear or legacy blending. 62 */ 63 AlphaOption fAlphaOption = AlphaOption::kIgnore; 64 SkTransferFunctionBehavior fBlendBehavior = SkTransferFunctionBehavior::kRespect; 65 }; 66 67 /** 68 * Encode the |src| pixels to the |dst| stream. 69 * |options| may be used to control the encoding behavior. 70 * 71 * Returns true on success. Returns false on an invalid or unsupported |src|. 72 */ 73 static bool Encode(SkWStream* dst, const SkPixmap& src, const Options& options); 74 75 /** 76 * Create a jpeg encoder that will encode the |src| pixels to the |dst| stream. 77 * |options| may be used to control the encoding behavior. 78 * 79 * |dst| is unowned but must remain valid for the lifetime of the object. 80 * 81 * This returns nullptr on an invalid or unsupported |src|. 82 */ 83 static std::unique_ptr<SkEncoder> Make(SkWStream* dst, const SkPixmap& src, 84 const Options& options); 85 86 ~SkJpegEncoder() override; 87 88 protected: 89 bool onEncodeRows(int numRows) override; 90 91 private: 92 SkJpegEncoder(std::unique_ptr<SkJpegEncoderMgr>, const SkPixmap& src); 93 94 std::unique_ptr<SkJpegEncoderMgr> fEncoderMgr; 95 typedef SkEncoder INHERITED; 96 }; 97 98 #endif 99