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ARGBAttenuate and ARGBUnattenuate for converting to/from attentuated ARGB

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BUG=none
TEST=none
Review URL: https://webrtc-codereview.appspot.com/490008

git-svn-id: http://libyuv.googlecode.com/svn/trunk@240 16f28f9a-4ce2-e073-06de-1de4eb20be90
This commit is contained in:
fbarchard@google.com 2012-04-17 00:49:28 +00:00
parent 96af870c8a
commit 829e7ea402
4 changed files with 111 additions and 2 deletions
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2
README.chromium
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@ -1,6 +1,6 @@
Name: libyuv
URL: http://code.google.com/p/libyuv/
Version: 239
Version: 240
License: BSD
License File: LICENSE

10
include/libyuv/planar_functions.h
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@ -160,6 +160,16 @@ int I422ToUYVY(const uint8* src_y, int src_stride_y,
uint8* dst_frame, int dst_stride_frame,
int width, int height);
// Convert unattentuated ARGB values to preattenuated ARGB.
int ARGBAttenuate(const uint8* src_argb, int src_stride_argb,
uint8* dst_argb, int dst_stride_argb,
int width, int height);
// Convert preattentuated ARGB values to unattenuated ARGB.
int ARGBUnattenuate(const uint8* src_argb, int src_stride_argb,
uint8* dst_argb, int dst_stride_argb,
int width, int height);
#ifdef __cplusplus
} // extern "C"
} // namespace libyuv

2
include/libyuv/version.h
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@ -11,7 +11,7 @@
#ifndef INCLUDE_LIBYUV_VERSION_H_
#define INCLUDE_LIBYUV_VERSION_H_
#define LIBYUV_VERSION 239
#define LIBYUV_VERSION 240
#endif // INCLUDE_LIBYUV_VERSION_H_

99
source/planar_functions.cc
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@ -863,6 +863,105 @@ int ARGBRect(uint8* dst_argb, int dst_stride_argb,
return 0;
}
// Multiply source RGB by alpha and store to destination.
static void ARGBAttenuateRow_C(const uint8* src_argb, uint8* dst_argb,
int width) {
for (int i = 0; i < width; ++i) {
const uint32 b = src_argb[0];
const uint32 g = src_argb[1];
const uint32 r = src_argb[2];
const uint32 a = src_argb[3];
dst_argb[0] = (b * a + 128) / 255;
dst_argb[1] = (g * a + 128) / 255;
dst_argb[2] = (r * a + 128) / 255;
dst_argb[3] = a;
src_argb += 4;
dst_argb += 4;
}
}
// Convert unattentuated ARGB values to preattenuated ARGB by multiplying RGB by
// by alpha.
// An unattenutated ARGB alpha blend uses the formula
// p = a * f + (1 - a) * b
// where
// p is output pixel
// f is foreground pixel
// b is background pixel
// a is alpha value from foreground pixel
// An preattenutated ARGB alpha blend uses the formula
// p = f + (1 - a) * b
// where
// f is foreground pixel premultiplied by alpha
int ARGBAttenuate(const uint8* src_argb, int src_stride_argb,
uint8* dst_argb, int dst_stride_argb,
int width, int height) {
if (height < 0) {
height = -height;
src_argb = src_argb + (height - 1) * src_stride_argb;
src_stride_argb = -src_stride_argb;
}
for (int y = 0; y < height; ++y) {
ARGBAttenuateRow_C(src_argb, dst_argb, width);
src_argb += src_stride_argb;
dst_argb += dst_stride_argb;
}
return 0;
}
// Divide source RGB by alpha and store to destination.
static void ARGBUnattenuateRow_C(const uint8* src_argb, uint8* dst_argb,
int width) {
for (int i = 0; i < width; ++i) {
uint32 b = src_argb[0];
uint32 g = src_argb[1];
uint32 r = src_argb[2];
const uint32 a = src_argb[3];
if (a) {
b = (b * 255 + 127) / a;
if (b > 255) {
b = 255;
}
g = (g * 255 + 127) / a;
if (g > 255) {
g = 255;
}
r = (r * 255 + 127) / a;
if (r > 255) {
r = 255;
}
}
dst_argb[0] = b;
dst_argb[1] = g;
dst_argb[2] = r;
dst_argb[3] = a;
src_argb += 4;
dst_argb += 4;
}
}
// Convert unattentuated ARGB values to preattenuated ARGB by multiplying RGB by
// by alpha.
int ARGBUnattenuate(const uint8* src_argb, int src_stride_argb,
uint8* dst_argb, int dst_stride_argb,
int width, int height) {
if (height < 0) {
height = -height;
src_argb = src_argb + (height - 1) * src_stride_argb;
src_stride_argb = -src_stride_argb;
}
for (int y = 0; y < height; ++y) {
ARGBUnattenuateRow_C(src_argb, dst_argb, width);
src_argb += src_stride_argb;
dst_argb += dst_stride_argb;
}
return 0;
}
#ifdef __cplusplus
} // extern "C"
} // namespace libyuv