blob: df315983ea3afa5c6edb80a5750ccb9fc24c501a [file] [log] [blame]
epoger@google.comec3ed6a2011-07-28 14:26:00 +00001/*
2 * Copyright 2011 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 */
tfarina@chromium.orge4fafb12013-12-12 21:11:12 +00007
reed@android.comd66efc22009-03-03 18:35:18 +00008#include "SkColorPriv.h"
tfarina@chromium.org8f6884a2014-01-24 20:56:26 +00009#include "Test.h"
reed@android.comd66efc22009-03-03 18:35:18 +000010
11// our std SkAlpha255To256
12static int test_srcover0(unsigned dst, unsigned alpha) {
13 return alpha + SkAlphaMul(dst, SkAlpha255To256(255 - alpha));
14}
15
16// faster hack +1
17static int test_srcover1(unsigned dst, unsigned alpha) {
18 return alpha + SkAlphaMul(dst, 256 - alpha);
19}
20
21// slower "correct"
22static int test_srcover2(unsigned dst, unsigned alpha) {
23 return alpha + SkMulDiv255Round(dst, 255 - alpha);
24}
25
tfarina@chromium.orge4fafb12013-12-12 21:11:12 +000026DEF_TEST(SrcOver, reporter) {
reed@android.comd66efc22009-03-03 18:35:18 +000027 /* Here's the idea. Can we ensure that when we blend on top of an opaque
28 dst, that the result always stay's opaque (i.e. exactly 255)?
29 */
reed@android.com80e39a72009-04-02 16:59:40 +000030
reed@android.comd66efc22009-03-03 18:35:18 +000031 unsigned i;
32 int opaqueCounter0 = 0;
33 int opaqueCounter1 = 0;
34 int opaqueCounter2 = 0;
35 for (i = 0; i <= 255; i++) {
36 unsigned result0 = test_srcover0(0xFF, i);
37 unsigned result1 = test_srcover1(0xFF, i);
38 unsigned result2 = test_srcover2(0xFF, i);
39 opaqueCounter0 += (result0 == 0xFF);
40 opaqueCounter1 += (result1 == 0xFF);
41 opaqueCounter2 += (result2 == 0xFF);
42 }
43#if 0
halcanary7d571242016-02-24 17:59:16 -080044 INFOF(reporter, "---- opaque test: [%d %d %d]\n",
45 opaqueCounter0, opaqueCounter1, opaqueCounter2);
reed@android.comd66efc22009-03-03 18:35:18 +000046#endif
47 // we acknowledge that technique0 does not always return opaque
reed@android.com9781ca52009-04-14 14:28:22 +000048 REPORTER_ASSERT(reporter, opaqueCounter0 == 256);
reed@android.comd66efc22009-03-03 18:35:18 +000049 REPORTER_ASSERT(reporter, opaqueCounter1 == 256);
50 REPORTER_ASSERT(reporter, opaqueCounter2 == 256);
reed@android.com80e39a72009-04-02 16:59:40 +000051
reed@android.comd66efc22009-03-03 18:35:18 +000052 // Now ensure that we never over/underflow a byte
53 for (i = 0; i <= 255; i++) {
54 for (unsigned dst = 0; dst <= 255; dst++) {
55 unsigned r0 = test_srcover0(dst, i);
56 unsigned r1 = test_srcover1(dst, i);
57 unsigned r2 = test_srcover2(dst, i);
58 unsigned max = SkMax32(dst, i);
59 // ignore the known failure
60 if (dst != 255) {
61 REPORTER_ASSERT(reporter, r0 <= 255 && r0 >= max);
62 }
63 REPORTER_ASSERT(reporter, r1 <= 255 && r1 >= max);
64 REPORTER_ASSERT(reporter, r2 <= 255 && r2 >= max);
reed@android.com80e39a72009-04-02 16:59:40 +000065
reed@android.comd66efc22009-03-03 18:35:18 +000066#if 0
67 // this shows where r1 (faster) differs from r2 (more exact)
68 if (r1 != r2) {
halcanary7d571242016-02-24 17:59:16 -080069 INFOF(reporter, "--- dst=%d i=%d r1=%d r2=%d exact=%g\n",
70 dst, i, r1, r2, i + dst - dst*i/255.0f);
reed@android.comd66efc22009-03-03 18:35:18 +000071 }
72#endif
73 }
74 }
75}