1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef SKIA_EXT_IMAGE_OPERATIONS_H_ 6 #define SKIA_EXT_IMAGE_OPERATIONS_H_ 7 8 #include "third_party/skia/include/core/SkBitmap.h" 9 #include "third_party/skia/include/core/SkTypes.h" 10 11 struct SkIRect; 12 13 namespace skia { 14 15 class SK_API ImageOperations { 16 public: 17 enum ResizeMethod { 18 // 19 // Quality Methods 20 // 21 // Those enumeration values express a desired quality/speed tradeoff. 22 // They are translated into an algorithm-specific method that depends 23 // on the capabilities (CPU, GPU) of the underlying platform. 24 // It is possible for all three methods to be mapped to the same 25 // algorithm on a given platform. 26 27 // Good quality resizing. Fastest resizing with acceptable visual quality. 28 // This is typically intended for use during interactive layouts 29 // where slower platforms may want to trade image quality for large 30 // increase in resizing performance. 31 // 32 // For example the resizing implementation may devolve to linear 33 // filtering if this enables GPU acceleration to be used. 34 // 35 // Note that the underlying resizing method may be determined 36 // on the fly based on the parameters for a given resize call. 37 // For example an implementation using a GPU-based linear filter 38 // in the common case may still use a higher-quality software-based 39 // filter in cases where using the GPU would actually be slower - due 40 // to too much latency - or impossible - due to image format or size 41 // constraints. 42 RESIZE_GOOD, 43 44 // Medium quality resizing. Close to high quality resizing (better 45 // than linear interpolation) with potentially some quality being 46 // traded-off for additional speed compared to RESIZE_BEST. 47 // 48 // This is intended, for example, for generation of large thumbnails 49 // (hundreds of pixels in each dimension) from large sources, where 50 // a linear filter would produce too many artifacts but where 51 // a RESIZE_HIGH might be too costly time-wise. 52 RESIZE_BETTER, 53 54 // High quality resizing. The algorithm is picked to favor image quality. 55 RESIZE_BEST, 56 57 // 58 // Algorithm-specific enumerations 59 // 60 61 // Box filter. This is a weighted average of all of the pixels touching 62 // the destination pixel. For enlargement, this is nearest neighbor. 63 // 64 // You probably don't want this, it is here for testing since it is easy to 65 // compute. Use RESIZE_LANCZOS3 instead. 66 RESIZE_BOX, 67 68 // 1-cycle Hamming filter. This is tall is the middle and falls off towards 69 // the window edges but without going to 0. This is about 40% faster than 70 // a 2-cycle Lanczos. 71 RESIZE_HAMMING1, 72 73 // 2-cycle Lanczos filter. This is tall in the middle, goes negative on 74 // each side, then returns to zero. Does not provide as good a frequency 75 // response as a 3-cycle Lanczos but is roughly 30% faster. 76 RESIZE_LANCZOS2, 77 78 // 3-cycle Lanczos filter. This is tall in the middle, goes negative on 79 // each side, then oscillates 2 more times. It gives nice sharp edges. 80 RESIZE_LANCZOS3, 81 82 // Lanczos filter + subpixel interpolation. If subpixel rendering is not 83 // appropriate we automatically fall back to Lanczos. 84 RESIZE_SUBPIXEL, 85 86 // enum aliases for first and last methods by algorithm or by quality. 87 RESIZE_FIRST_QUALITY_METHOD = RESIZE_GOOD, 88 RESIZE_LAST_QUALITY_METHOD = RESIZE_BEST, 89 RESIZE_FIRST_ALGORITHM_METHOD = RESIZE_BOX, 90 RESIZE_LAST_ALGORITHM_METHOD = RESIZE_SUBPIXEL, 91 }; 92 93 // Resizes the given source bitmap using the specified resize method, so that 94 // the entire image is (dest_size) big. The dest_subset is the rectangle in 95 // this destination image that should actually be returned. 96 // 97 // The output image will be (dest_subset.width(), dest_subset.height()). This 98 // will save work if you do not need the entire bitmap. 99 // 100 // The destination subset must be smaller than the destination image. 101 static SkBitmap Resize(const SkBitmap& source, 102 ResizeMethod method, 103 int dest_width, int dest_height, 104 const SkIRect& dest_subset, 105 SkBitmap::Allocator* allocator = NULL); 106 107 // Alternate version for resizing and returning the entire bitmap rather than 108 // a subset. 109 static SkBitmap Resize(const SkBitmap& source, 110 ResizeMethod method, 111 int dest_width, int dest_height, 112 SkBitmap::Allocator* allocator = NULL); 113 114 private: 115 ImageOperations(); // Class for scoping only. 116 117 // Supports all methods except RESIZE_SUBPIXEL. 118 static SkBitmap ResizeBasic(const SkBitmap& source, 119 ResizeMethod method, 120 int dest_width, int dest_height, 121 const SkIRect& dest_subset, 122 SkBitmap::Allocator* allocator = NULL); 123 124 // Subpixel renderer. 125 static SkBitmap ResizeSubpixel(const SkBitmap& source, 126 int dest_width, int dest_height, 127 const SkIRect& dest_subset, 128 SkBitmap::Allocator* allocator = NULL); 129 }; 130 131 } // namespace skia 132 133 #endif // SKIA_EXT_IMAGE_OPERATIONS_H_ 134
