1 /*
2 * Copyright 2013 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 SkMatrixUtils_DEFINED
9 #define SkMatrixUtils_DEFINED
10
11 #include "SkMatrix.h"
12
13 /**
14 * Number of subpixel bits used in skia's bilerp.
15 * See SkBitmapProcState_procs.h and SkBitmapProcState_filter.h
16 */
17 #define kSkSubPixelBitsForBilerp 4
18
19 /**
20 * Given a matrix and width/height, return true if the computed dst-rect would
21 * align such that there is a 1-to-1 coorspondence between src and dst pixels.
22 * This can be called by drawing code to see if drawBitmap can be turned into
23 * drawSprite (which is faster).
24 *
25 * The src-rect is defined to be { 0, 0, width, height }
26 *
27 * The "closeness" test is based on the subpixelBits parameter. Pass 0 for
28 * round-to-nearest behavior (e.g. nearest neighbor sampling). Pass the number
29 * of subpixel-bits to simulate filtering.
30 */
31 bool SkTreatAsSprite(const SkMatrix&, int width, int height,
32 unsigned subpixelBits);
33
34 /**
35 * Calls SkTreatAsSprite() with default subpixelBits value to match Skia's
36 * filter-bitmap implementation (i.e. kSkSubPixelBitsForBilerp).
37 */
SkTreatAsSpriteFilter(const SkMatrix & matrix,int width,int height)38 static inline bool SkTreatAsSpriteFilter(const SkMatrix& matrix,
39 int width, int height) {
40 return SkTreatAsSprite(matrix, width, height, kSkSubPixelBitsForBilerp);
41 }
42
43 /** Decomposes the upper-left 2x2 of the matrix into a rotation (represented by
44 the cosine and sine of the rotation angle), followed by a non-uniform scale,
45 followed by another rotation. If there is a reflection, one of the scale
46 factors will be negative.
47 Returns true if successful. Returns false if the matrix is degenerate.
48 */
49 bool SkDecomposeUpper2x2(const SkMatrix& matrix,
50 SkPoint* rotation1,
51 SkPoint* scale,
52 SkPoint* rotation2);
53
54 #endif
55