skia2/tests/BlendTest.cpp
Mike Reed 0e39f97cd7 Revert "Revert "make it illegal to include SkXfermode.h""
This reverts commit e9d1b299cc.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Revert "make it illegal to include SkXfermode.h"
> 
> This reverts commit 07764cefbb.
> 
> Reason for revert: breaking google3
> 
> Original change's description:
> > make it illegal to include SkXfermode.h
> > 
> > BUG=skia:
> > 
> > GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5133
> > 
> > Change-Id: I6e8596dcb17cd7e8efa67859bb682bf9bfcac4db
> > Reviewed-on: https://skia-review.googlesource.com/5133
> > Reviewed-by: Mike Reed <reed@google.com>
> > Commit-Queue: Mike Reed <reed@google.com>
> > 
> 
> TBR=reed@google.com,reviews@skia.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> 
> Change-Id: I136f9e533eb60633c49dffa19b5747d50b6d98a8
> Reviewed-on: https://skia-review.googlesource.com/5196
> Commit-Queue: Greg Daniel <egdaniel@google.com>
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> 

TBR=egdaniel@google.com,reviews@skia.org,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I0b767ce778a4ade83c2f07d5ece486bb46d7712c
Reviewed-on: https://skia-review.googlesource.com/5223
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Reed <reed@google.com>
2016-11-23 22:17:17 +00:00

69 lines
2.3 KiB
C++

/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "Test.h"
#include "SkColor.h"
#include "SkColorPriv.h"
#include "SkTaskGroup.h"
#include <functional>
struct Results { int diffs, diffs_0x00, diffs_0xff, diffs_by_1; };
static bool acceptable(const Results& r) {
#if 0
SkDebugf("%d diffs, %d at 0x00, %d at 0xff, %d off by 1, all out of 65536\n",
r.diffs, r.diffs_0x00, r.diffs_0xff, r.diffs_by_1);
#endif
return r.diffs_by_1 == r.diffs // never off by more than 1
&& r.diffs_0x00 == 0 // transparent must stay transparent
&& r.diffs_0xff == 0; // opaque must stay opaque
}
template <typename Fn>
static Results test(Fn&& multiply) {
Results r = { 0,0,0,0 };
for (int x = 0; x < 256; x++) {
for (int y = 0; y < 256; y++) {
int p = multiply(x, y),
ideal = (x*y+127)/255;
if (p != ideal) {
r.diffs++;
if (x == 0x00 || y == 0x00) { r.diffs_0x00++; }
if (x == 0xff || y == 0xff) { r.diffs_0xff++; }
if (SkTAbs(ideal - p) == 1) { r.diffs_by_1++; }
}
}}
return r;
}
DEF_TEST(Blend_byte_multiply, r) {
// These are all temptingly close but fundamentally broken.
int (*broken[])(int, int) = {
[](int x, int y) { return (x*y)>>8; },
[](int x, int y) { return (x*y+128)>>8; },
[](int x, int y) { y += y>>7; return (x*y)>>8; },
};
for (auto multiply : broken) { REPORTER_ASSERT(r, !acceptable(test(multiply))); }
// These are fine to use, but not perfect.
int (*fine[])(int, int) = {
[](int x, int y) { return (x*y+x)>>8; },
[](int x, int y) { return (x*y+y)>>8; },
[](int x, int y) { return (x*y+255)>>8; },
[](int x, int y) { y += y>>7; return (x*y+128)>>8; },
};
for (auto multiply : fine) { REPORTER_ASSERT(r, acceptable(test(multiply))); }
// These are pefect.
int (*perfect[])(int, int) = {
[](int x, int y) { return (x*y+127)/255; }, // Duh.
[](int x, int y) { int p = (x*y+128); return (p+(p>>8))>>8; },
[](int x, int y) { return ((x*y+128)*257)>>16; },
};
for (auto multiply : perfect) { REPORTER_ASSERT(r, test(multiply).diffs == 0); }
}