1 /*
2 * Copyright 2020 Google LLC
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 #include "include/core/SkCanvas.h"
9 #include "include/core/SkSurface.h"
10 #include "include/utils/SkRandom.h"
11 #include "src/core/SkSamplingPriv.h"
12 #include "tests/Test.h"
13 #include "tools/Resources.h"
14 #include "tools/ToolUtils.h"
15
16 // In general, sampling under identity matrix should not affect the pixels. However,
17 // cubic resampling when B != 0 is expected to change pixels.
18 //
DEF_TEST(sampling_with_identity_matrix,r)19 DEF_TEST(sampling_with_identity_matrix, r) {
20 const char* names[] = {
21 "images/mandrill_128.png", "images/color_wheel.jpg",
22 };
23
24 SkRandom rand;
25 for (auto name : names) {
26 auto src = GetResourceAsImage(name);
27 auto surf = SkSurface::MakeRasterN32Premul(src->width(), src->height());
28 auto canvas = surf->getCanvas();
29
30 auto dotest = [&](const SkSamplingOptions& sampling, bool expect_same) {
31 canvas->clear(0);
32 canvas->drawImage(src.get(), 0, 0, sampling, nullptr);
33 auto dst = surf->makeImageSnapshot();
34
35 REPORTER_ASSERT(r, SkSamplingPriv::NoChangeWithIdentityMatrix(sampling) == expect_same);
36 REPORTER_ASSERT(r, ToolUtils::equal_pixels(src.get(), dst.get()) == expect_same);
37 };
38
39 // Exercise all non-cubics -- expecting no changes
40 for (auto m : {SkMipmapMode::kNone, SkMipmapMode::kNearest, SkMipmapMode::kLinear}) {
41 for (auto f : {SkFilterMode::kNearest, SkFilterMode::kLinear}) {
42 dotest(SkSamplingOptions(f, m), true);
43 }
44 }
45
46 // Exercise cubic variants with B zero and non-zero
47 constexpr int N = 30; // try a bunch of random values
48 for (int i = 0; i < N; ++i) {
49 float C = rand.nextF();
50 dotest(SkSamplingOptions({0, C}), true);
51
52 float B = rand.nextF() * 0.9f + 0.05f; // non-zero but still within (0,,,1]
53 SkASSERT(B != 0);
54 dotest(SkSamplingOptions({B, C}), false);
55 }
56 }
57 }
58
