// Copyright 2014 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// WebPPicture tools: alpha handling, etc.
//
// Author: Skal (pascal.massimino@gmail.com)
#include <assert.h>
#include "src/enc/vp8i_enc.h"
#include "src/dsp/yuv.h"
//------------------------------------------------------------------------------
// Helper: clean up fully transparent area to help compressibility.
#define SIZE 8
#define SIZE2 (SIZE / 2)
static int IsTransparentARGBArea(
const uint32_t* ptr,
int stride,
int size) {
int y, x;
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
if (ptr[x] & 0xff000000u) {
return 0;
}
}
ptr += stride;
}
return 1;
}
static void Flatten(uint8_t* ptr,
int v,
int stride,
int size) {
int y;
for (y = 0; y < size; ++y) {
memset(ptr, v, size);
ptr += stride;
}
}
static void FlattenARGB(uint32_t* ptr, uint32_t v,
int stride,
int size) {
int x, y;
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) ptr[x] = v;
ptr += stride;
}
}
// Smoothen the luma components of transparent pixels. Return true if the whole
// block is transparent.
static int SmoothenBlock(
const uint8_t* a_ptr,
int a_stride, uint8_t* y_ptr,
int y_stride,
int width,
int height) {
int sum = 0, count = 0;
int x, y;
const uint8_t* alpha_ptr = a_ptr;
uint8_t* luma_ptr = y_ptr;
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
if (alpha_ptr[x] != 0) {
++count;
sum += luma_ptr[x];
}
}
alpha_ptr += a_stride;
luma_ptr += y_stride;
}
if (count > 0 && count < width * height) {
const uint8_t avg_u8 = (uint8_t)(sum / count);
alpha_ptr = a_ptr;
luma_ptr = y_ptr;
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
if (alpha_ptr[x] == 0) luma_ptr[x] = avg_u8;
}
alpha_ptr += a_stride;
luma_ptr += y_stride;
}
}
return (count == 0);
}
void WebPReplaceTransparentPixels(WebPPicture*
const pic, uint32_t color) {
if (pic != NULL && pic->use_argb) {
int y = pic->height;
uint32_t* argb = pic->argb;
color &= 0xffffffu;
// force alpha=0
WebPInitAlphaProcessing();
while (y-- > 0) {
WebPAlphaReplace(argb, pic->width, color);
argb += pic->argb_stride;
}
}
}
void WebPCleanupTransparentArea(WebPPicture* pic) {
int x, y, w, h;
if (pic == NULL)
return;
w = pic->width / SIZE;
h = pic->height / SIZE;
// note: we ignore the left-overs on right/bottom, except for SmoothenBlock().
if (pic->use_argb) {
uint32_t argb_value = 0;
for (y = 0; y < h; ++y) {
int need_reset = 1;
for (x = 0; x < w; ++x) {
const int off = (y * pic->argb_stride + x) * SIZE;
if (IsTransparentARGBArea(pic->argb + off, pic->argb_stride, SIZE)) {
if (need_reset) {
argb_value = pic->argb[off];
need_reset = 0;
}
FlattenARGB(pic->argb + off, argb_value, pic->argb_stride, SIZE);
}
else {
need_reset = 1;
}
}
}
}
else {
const int width = pic->width;
const int height = pic->height;
const int y_stride = pic->y_stride;
const int uv_stride = pic->uv_stride;
const int a_stride = pic->a_stride;
uint8_t* y_ptr = pic->y;
uint8_t* u_ptr = pic->u;
uint8_t* v_ptr = pic->v;
const uint8_t* a_ptr = pic->a;
int values[3] = { 0 };
if (a_ptr == NULL || y_ptr == NULL || u_ptr == NULL || v_ptr == NULL) {
return;
}
for (y = 0; y + SIZE <= height; y += SIZE) {
int need_reset = 1;
for (x = 0; x + SIZE <= width; x += SIZE) {
if (SmoothenBlock(a_ptr + x, a_stride, y_ptr + x, y_stride,
SIZE, SIZE)) {
if (need_reset) {
values[0] = y_ptr[x];
values[1] = u_ptr[x >> 1];
values[2] = v_ptr[x >> 1];
need_reset = 0;
}
Flatten(y_ptr + x, values[0], y_stride, SIZE);
Flatten(u_ptr + (x >> 1), values[1], uv_stride, SIZE2);
Flatten(v_ptr + (x >> 1), values[2], uv_stride, SIZE2);
}
else {
need_reset = 1;
}
}
if (x < width) {
SmoothenBlock(a_ptr + x, a_stride, y_ptr + x, y_stride,
width - x, SIZE);
}
a_ptr += SIZE * a_stride;
y_ptr += SIZE * y_stride;
u_ptr += SIZE2 * uv_stride;
v_ptr += SIZE2 * uv_stride;
}
if (y < height) {
const int sub_height = height - y;
for (x = 0; x + SIZE <= width; x += SIZE) {
SmoothenBlock(a_ptr + x, a_stride, y_ptr + x, y_stride,
SIZE, sub_height);
}
if (x < width) {
SmoothenBlock(a_ptr + x, a_stride, y_ptr + x, y_stride,
width - x, sub_height);
}
}
}
}
#undef SIZE
#undef SIZE2
//------------------------------------------------------------------------------
// Blend color and remove transparency info
#define BLEND(V0, V1, ALPHA) \
((((V0) * (255 - (ALPHA)) + (V1) * (ALPHA)) * 0x101 + 256) >> 16)
#define BLEND_10BIT(V0, V1, ALPHA) \
((((V0) * (1020 - (ALPHA)) + (V1) * (ALPHA)) * 0x101 + 1024) >> 18)
static WEBP_INLINE uint32_t MakeARGB32(
int r,
int g,
int b) {
return (0xff000000u | (r << 16) | (g << 8) | b);
}
void WebPBlendAlpha(WebPPicture* picture, uint32_t background_rgb) {
const int red = (background_rgb >> 16) & 0xff;
const int green = (background_rgb >> 8) & 0xff;
const int blue = (background_rgb >> 0) & 0xff;
int x, y;
if (picture == NULL)
return;
if (!picture->use_argb) {
// omit last pixel during u/v loop
const int uv_width = (picture->width >> 1);
const int Y0 = VP8RGBToY(red, green, blue, YUV_HALF);
// VP8RGBToU/V expects the u/v values summed over four pixels
const int U0 = VP8RGBToU(4 * red, 4 * green, 4 * blue, 4 * YUV_HALF);
const int V0 = VP8RGBToV(4 * red, 4 * green, 4 * blue, 4 * YUV_HALF);
const int has_alpha = picture->colorspace & WEBP_CSP_ALPHA_BIT;
uint8_t* y_ptr = picture->y;
uint8_t* u_ptr = picture->u;
uint8_t* v_ptr = picture->v;
uint8_t* a_ptr = picture->a;
if (!has_alpha || a_ptr == NULL)
return;
// nothing to do
for (y = 0; y < picture->height; ++y) {
// Luma blending
for (x = 0; x < picture->width; ++x) {
const uint8_t alpha = a_ptr[x];
if (alpha < 0xff) {
y_ptr[x] = BLEND(Y0, y_ptr[x], alpha);
}
}
// Chroma blending every even line
if ((y & 1) == 0) {
uint8_t*
const a_ptr2 =
(y + 1 == picture->height) ? a_ptr : a_ptr + picture->a_stride;
for (x = 0; x < uv_width; ++x) {
// Average four alpha values into a single blending weight.
// TODO(skal): might lead to visible contouring. Can we do better?
const uint32_t alpha =
a_ptr[2 * x + 0] + a_ptr[2 * x + 1] +
a_ptr2[2 * x + 0] + a_ptr2[2 * x + 1];
u_ptr[x] = BLEND_10BIT(U0, u_ptr[x], alpha);
v_ptr[x] = BLEND_10BIT(V0, v_ptr[x], alpha);
}
if (picture->width & 1) {
// rightmost pixel
const uint32_t alpha = 2 * (a_ptr[2 * x + 0] + a_ptr2[2 * x + 0]);
u_ptr[x] = BLEND_10BIT(U0, u_ptr[x], alpha);
v_ptr[x] = BLEND_10BIT(V0, v_ptr[x], alpha);
}
}
else {
u_ptr += picture->uv_stride;
v_ptr += picture->uv_stride;
}
memset(a_ptr, 0xff, picture->width);
// reset alpha value to opaque
a_ptr += picture->a_stride;
y_ptr += picture->y_stride;
}
}
else {
uint32_t* argb = picture->argb;
const uint32_t background = MakeARGB32(red, green, blue);
for (y = 0; y < picture->height; ++y) {
for (x = 0; x < picture->width; ++x) {
const int alpha = (argb[x] >> 24) & 0xff;
if (alpha != 0xff) {
if (alpha > 0) {
int r = (argb[x] >> 16) & 0xff;
int g = (argb[x] >> 8) & 0xff;
int b = (argb[x] >> 0) & 0xff;
r = BLEND(red, r, alpha);
g = BLEND(green, g, alpha);
b = BLEND(blue, b, alpha);
argb[x] = MakeARGB32(r, g, b);
}
else {
argb[x] = background;
}
}
}
argb += picture->argb_stride;
}
}
}
#undef BLEND
#undef BLEND_10BIT
//------------------------------------------------------------------------------
