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 */
31bool 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 */
38static 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    */
49bool SkDecomposeUpper2x2(const SkMatrix& matrix,
50                         SkPoint* rotation1,
51                         SkPoint* scale,
52                         SkPoint* rotation2);
53
54#endif
55