Index: skia/ext/image_operations.h |
=================================================================== |
--- skia/ext/image_operations.h (revision 68621) |
+++ skia/ext/image_operations.h (working copy) |
@@ -1,4 +1,4 @@ |
-// Copyright (c) 2009 The Chromium Authors. All rights reserved. |
+// Copyright (c) 2010 The Chromium Authors. All rights reserved. |
// Use of this source code is governed by a BSD-style license that can be |
// found in the LICENSE file. |
@@ -14,6 +14,49 @@ |
class ImageOperations { |
public: |
enum ResizeMethod { |
+ // |
+ // Quality Methods |
+ // |
+ // Those enumeration values express a desired quality/speed tradeoff. |
+ // They are translated into an algorithm-specific method that depends |
+ // on the capabilities (CPU, GPU) of the underlying platform. |
+ // It is possible for all three methods to be mapped to the same |
+ // algorithm on a given platform. |
+ |
+ // Good quality resizing. Fastest resizing with acceptable visual quality. |
+ // This is typically intended for use during interactive layouts |
+ // where slower platforms may want to trade image quality for large |
+ // increase in resizing performance. |
+ // |
+ // For example the resizing implementation may devolve to linear |
+ // filtering if this enables GPU acceleration to be used. |
+ // |
+ // Note that the underlying resizing method may be determined |
+ // on the fly based on the parameters for a given resize call. |
+ // For example an implementation using a GPU-based linear filter |
+ // in the common case may still use a higher-quality software-based |
+ // filter in cases where using the GPU would actually be slower - due |
+ // to too much latency - or impossible - due to image format or size |
+ // constraints. |
+ RESIZE_GOOD, |
+ |
+ // Medium quality resizing. Close to high quality resizing (better |
+ // than linear interpolation) with potentially some quality being |
+ // traded-off for additional speed compared to RESIZE_BEST. |
+ // |
+ // This is intended, for example, for generation of large thumbnails |
+ // (hundreds of pixels in each dimension) from large sources, where |
+ // a linear filter would produce too many artifacts but where |
+ // a RESIZE_HIGH might be too costly time-wise. |
+ RESIZE_BETTER, |
+ |
+ // High quality resizing. The algorithm is picked to favor image quality. |
+ RESIZE_BEST, |
+ |
+ // |
+ // Algorithm-specific enumerations |
+ // |
+ |
// Box filter. This is a weighted average of all of the pixels touching |
// the destination pixel. For enlargement, this is nearest neighbor. |
// |
@@ -21,6 +64,21 @@ |
// compute. Use RESIZE_LANCZOS3 instead. |
RESIZE_BOX, |
+ // 1-cycle Hamming filter. This is tall is the middle and falls off towards |
+ // the window edges but without going to 0. This is about 40% faster than |
+ // a 2-cycle Lanczos. |
+ RESIZE_HAMMING1, |
+ |
+ // 2-cycle Lanczos filter. This is tall in the middle, goes negative on |
brettw
2010/12/17 20:07:55
This comment looks wrong (it's the same as the 2-c
evannier
2010/12/19 00:15:03
Done. Indeed, as mentioned in the .cc, LANCZOS1 is
|
+ // each side, then returns to zero. Does not provide as good a frequency |
+ // response as a 3-cycle Lanczos but is roughly 30% faster. |
+ RESIZE_LANCZOS1, |
+ |
+ // 2-cycle Lanczos filter. This is tall in the middle, goes negative on |
+ // each side, then returns to zero. Does not provide as good a frequency |
+ // response as a 3-cycle Lanczos but is roughly 30% faster. |
+ RESIZE_LANCZOS2, |
+ |
// 3-cycle Lanczos filter. This is tall in the middle, goes negative on |
// each side, then oscillates 2 more times. It gives nice sharp edges. |
RESIZE_LANCZOS3, |
@@ -28,6 +86,12 @@ |
// Lanczos filter + subpixel interpolation. If subpixel rendering is not |
// appropriate we automatically fall back to Lanczos. |
RESIZE_SUBPIXEL, |
+ |
+ // |
+ RESIZE_FIRST_QUALITY_METHOD = RESIZE_GOOD, |
+ RESIZE_LAST_QUALITY_METHOD = RESIZE_BEST, |
+ RESIZE_FIRST_ALGORITHM_METHOD = RESIZE_BOX, |
+ RESIZE_LAST_ALGORITHM_METHOD = RESIZE_SUBPIXEL, |
}; |
// Resizes the given source bitmap using the specified resize method, so that |