// 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 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

void WebPCleanupTransparentAreaLossless(WebPPicture* const pic) {

int x, y, w, h;

uint32_t* argb;

assert(pic != NULL && pic->use_argb);

w = pic->width;

h = pic->height;

argb = pic->argb;

for (y = 0; y < h; ++y) {

for (x = 0; x < w; ++x) {

if ((argb[x] & 0xff000000) == 0) {

argb[x] = 0x00000000;

}

}

argb += pic->argb_stride;

}

}

//------------------------------------------------------------------------------

// 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* pic, 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 (pic == NULL) return;

if (!pic->use_argb) {

const int uv_width = (pic->width >> 1); // omit last pixel during u/v loop

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 = pic->colorspace & WEBP_CSP_ALPHA_BIT;

uint8_t* y_ptr = pic->y;

uint8_t* u_ptr = pic->u;

uint8_t* v_ptr = pic->v;

uint8_t* a_ptr = pic->a;

if (!has_alpha || a_ptr == NULL) return; // nothing to do

for (y = 0; y < pic->height; ++y) {

// Luma blending

for (x = 0; x < pic->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 == pic->height) ? a_ptr : a_ptr + pic->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 (pic->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 += pic->uv_stride;

v_ptr += pic->uv_stride;

}

memset(a_ptr, 0xff, pic->width); // reset alpha value to opaque

a_ptr += pic->a_stride;

y_ptr += pic->y_stride;

}

} else {

uint32_t* argb = pic->argb;

const uint32_t background = MakeARGB32(red, green, blue);

for (y = 0; y < pic->height; ++y) {

for (x = 0; x < pic->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 += pic->argb_stride;

}

}

}

#undef BLEND

#undef BLEND_10BIT

//------------------------------------------------------------------------------