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add automatic YUVA/ARGB conversion during WebPEncode()

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Adds new methods WebPPictureARGBToYUVA() and WebPPictureYUVAToARGB()
Depending on the value of picture->use_argb_input,
the main call WebPEncode() will convert appropriately.
Note that both conversions are lossy, so it's recommended to:
* use YUVA input for lossy compression (picture->use_argb_input=0)
* use ARGB input for lossless compression (picture->use_argb_input=1)

Change-Id: I8269d607723ee8a1136b9f4999f7ff4e657bbb04
This commit is contained in:
Pascal Massimino 2012-06-28 00:34:23 -07:00
parent 802e012a18
commit fcc69923b9
5 changed files with 378 additions and 137 deletions
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7
src/dsp/dsp.h
View File

@ -145,13 +145,13 @@ void VP8DspInit(void);
#define FANCY_UPSAMPLING // undefined to remove fancy upsampling support
#ifdef FANCY_UPSAMPLING
typedef void (*WebPUpsampleLinePairFunc)(
const uint8_t* top_y, const uint8_t* bottom_y,
const uint8_t* top_u, const uint8_t* top_v,
const uint8_t* cur_u, const uint8_t* cur_v,
uint8_t* top_dst, uint8_t* bottom_dst, int len);
#ifdef FANCY_UPSAMPLING
// Fancy upsampling functions to convert YUV to RGB(A) modes
extern WebPUpsampleLinePairFunc WebPUpsamplers[/* MODE_LAST */];
@ -169,6 +169,11 @@ typedef void (*WebPSampleLinePairFunc)(
extern const WebPSampleLinePairFunc WebPSamplers[/* MODE_LAST */];
// General function for converting two lines of ARGB or RGBA.
// 'alpha_is_last' should be true if 0xff000000 is stored in memory as
// as 0x00, 0x00, 0x00, 0xff (little endian).
WebPUpsampleLinePairFunc WebPGetLinePairConverter(int alpha_is_last);
// YUV444->RGB converters
typedef void (*WebPYUV444Converter)(const uint8_t* y,
const uint8_t* u, const uint8_t* v,

42
src/dsp/upsampling.c
View File

@ -156,6 +156,48 @@ const WebPSampleLinePairFunc WebPSamplers[MODE_LAST] = {
SampleRgba4444LinePair // MODE_rgbA_4444
};
//------------------------------------------------------------------------------
#if !defined(FANCY_UPSAMPLING)
#define DUAL_SAMPLE_FUNC(FUNC_NAME, FUNC) \
static void FUNC_NAME(const uint8_t* top_y, const uint8_t* bot_y, \
const uint8_t* top_u, const uint8_t* top_v, \
const uint8_t* bot_u, const uint8_t* bot_v, \
uint8_t* top_dst, uint8_t* bot_dst, int len) { \
const int half_len = len >> 1; \
int x; \
if (top_dst != NULL) { \
for (x = 0; x < half_len; ++x) { \
FUNC(top_y[2 * x + 0], top_u[x], top_v[x], top_dst + 8 * x + 0); \
FUNC(top_y[2 * x + 1], top_u[x], top_v[x], top_dst + 8 * x + 4); \
} \
if (len & 1) FUNC(top_y[2 * x + 0], top_u[x], top_v[x], top_dst + 8 * x); \
} \
if (bot_dst != NULL) { \
for (x = 0; x < half_len; ++x) { \
FUNC(bot_y[2 * x + 0], bot_u[x], bot_v[x], bot_dst + 8 * x + 0); \
FUNC(bot_y[2 * x + 1], bot_u[x], bot_v[x], bot_dst + 8 * x + 4); \
} \
if (len & 1) FUNC(bot_y[2 * x + 0], bot_u[x], bot_v[x], bot_dst + 8 * x); \
} \
}
DUAL_SAMPLE_FUNC(DualLineSamplerBGRA, VP8YuvToBgra)
DUAL_SAMPLE_FUNC(DualLineSamplerARGB, VP8YuvToArgb)
#undef DUAL_SAMPLE_FUNC
#endif // !FANCY_UPSAMPLING
WebPUpsampleLinePairFunc WebPGetLinePairConverter(int alpha_is_last) {
WebPInitUpsamplers();
VP8YUVInit();
#ifdef FANCY_UPSAMPLING
return WebPUpsamplers[alpha_is_last ? MODE_BGRA : MODE_ARGB];
#else
return (alpha_is_last ? DualLineSamplerBGRA : DualLineSamplerARGB);
#endif
}
//------------------------------------------------------------------------------
// YUV444 converter

428
src/enc/picture.c
View File

@ -15,6 +15,7 @@
#include "./vp8enci.h"
#include "../utils/rescaler.h"
#include "../dsp/dsp.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
@ -23,6 +24,12 @@ extern "C" {
#define HALVE(x) (((x) + 1) >> 1)
#define IS_YUV_CSP(csp, YUV_CSP) (((csp) & WEBP_CSP_UV_MASK) == (YUV_CSP))
static const union {
uint32_t argb;
uint8_t bytes[4];
} test_endian = { 0xff000000u };
#define ALPHA_IS_LAST (test_endian.bytes[3] == 0xff)
//------------------------------------------------------------------------------
// WebPPicture
//------------------------------------------------------------------------------
@ -79,16 +86,17 @@ int WebPPictureAlloc(WebPPicture* const picture) {
(size_t)total_size != total_size) { // overflow on 32bit
return 0;
}
picture->y_stride = y_stride;
picture->uv_stride = uv_stride;
picture->a_stride = a_stride;
picture->uv0_stride = uv0_stride;
// Clear previous buffer and allocate a new one.
WebPPictureFree(picture); // erase previous buffer
mem = (uint8_t*)malloc((size_t)total_size);
if (mem == NULL) return 0;
// From now on, we're in the clear, we can no longer fail...
picture->memory_ = (void*)mem;
picture->y_stride = y_stride;
picture->uv_stride = uv_stride;
picture->a_stride = a_stride;
picture->uv0_stride = uv0_stride;
// TODO(skal): we could align the y/u/v planes and adjust stride.
picture->y = mem;
mem += y_size;
@ -117,12 +125,13 @@ int WebPPictureAlloc(WebPPicture* const picture) {
(size_t)total_size != total_size) {
return 0;
}
// Clear previous buffer and allocate a new one.
WebPPictureFree(picture); // erase previous buffer
memory = malloc((size_t)total_size);
if (memory == NULL) return 0;
picture->memory_argb_ = memory;
// TODO(skal): align plane to cache line?
picture->memory_argb_ = memory;
picture->argb = (uint32_t*)memory;
picture->argb_stride = width;
}
@ -130,26 +139,57 @@ int WebPPictureAlloc(WebPPicture* const picture) {
return 1;
}
// Grab the 'specs' (writer, *opaque, width, height...) from 'src' and copy them
// into 'dst'. Mark 'dst' as not owning any memory. 'src' can be NULL.
static void WebPPictureGrabSpecs(const WebPPicture* const src,
WebPPicture* const dst) {
assert(dst != NULL);
if (src != NULL) *dst = *src;
dst->y = dst->u = dst->v = NULL;
dst->u0 = dst->v0 = NULL;
dst->a = NULL;
dst->argb = NULL;
dst->memory_ = NULL;
dst->memory_argb_ = NULL;
// Remove reference to the ARGB buffer (doesn't free anything).
static void PictureResetARGB(WebPPicture* const picture) {
picture->memory_argb_ = NULL;
picture->argb = NULL;
picture->argb_stride = 0;
}
// Release memory owned by 'picture'.
// Remove reference to the YUVA buffer (doesn't free anything).
static void PictureResetYUVA(WebPPicture* const picture) {
picture->memory_ = NULL;
picture->y = picture->u = picture->v = picture->a = NULL;
picture->u0 = picture->v0 = NULL;
picture->y_stride = picture->uv_stride = 0;
picture->a_stride = 0;
picture->uv0_stride = 0;
}
// Grab the 'specs' (writer, *opaque, width, height...) from 'src' and copy them
// into 'dst'. Mark 'dst' as not owning any memory.
static void WebPPictureGrabSpecs(const WebPPicture* const src,
WebPPicture* const dst) {
assert(src != NULL && dst != NULL);
*dst = *src;
PictureResetYUVA(dst);
PictureResetARGB(dst);
}
// Allocate a new argb buffer, discarding any existing one and preserving
// the other YUV(A) buffer.
static int PictureAllocARGB(WebPPicture* const picture) {
WebPPicture tmp;
free(picture->memory_argb_);
PictureResetARGB(picture);
picture->use_argb_input = 1;
WebPPictureGrabSpecs(picture, &tmp);
if (!WebPPictureAlloc(&tmp)) {
return WebPEncodingSetError(picture, VP8_ENC_ERROR_OUT_OF_MEMORY);
}
picture->memory_argb_ = tmp.memory_argb_;
picture->argb = tmp.argb;
picture->argb_stride = tmp.argb_stride;
return 1;
}
// Release memory owned by 'picture' (both YUV and ARGB buffers).
void WebPPictureFree(WebPPicture* const picture) {
if (picture != NULL) {
free(picture->memory_);
free(picture->memory_argb_);
WebPPictureGrabSpecs(NULL, picture);
PictureResetYUVA(picture);
PictureResetARGB(picture);
}
}
@ -468,6 +508,43 @@ int WebPMemoryWrite(const uint8_t* data, size_t data_size,
return 1;
}
//------------------------------------------------------------------------------
// Detection of non-trivial transparency
// Returns true if alpha[] has non-0xff values.
static int CheckNonOpaque(const uint8_t* alpha, int width, int height,
int x_step, int y_step) {
if (alpha == NULL) return 0;
while (height-- > 0) {
int x;
for (x = 0; x < width * x_step; x += x_step) {
if (alpha[x] != 0xff) return 1; // TODO(skal): check 4/8 bytes at a time.
}
alpha += y_step;
}
return 0;
}
// Checking for the presence of non-opaque alpha.
int WebPPictureHasTransparency(const WebPPicture* const picture) {
if (picture == NULL) return 0;
if (!picture->use_argb_input) {
return CheckNonOpaque(picture->a, picture->width, picture->height,
1, picture->a_stride);
} else {
int x, y;
const uint32_t* argb = picture->argb;
if (argb == NULL) return 0;
for (y = 0; y < picture->height; ++y) {
for (x = 0; x < picture->width; ++x) {
if (argb[x] < 0xff000000u) return 1; // test any alpha values != 0xff
}
argb += picture->argb_stride;
}
}
return 0;
}
//------------------------------------------------------------------------------
// RGB -> YUV conversion
// The exact naming is Y'CbCr, following the ITU-R BT.601 standard.
@ -534,17 +611,103 @@ static void MakeGray(WebPPicture* const picture) {
}
}
static int ImportYUVAFromRGBA(const uint8_t* const r_ptr,
const uint8_t* const g_ptr,
const uint8_t* const b_ptr,
const uint8_t* const a_ptr,
int step, // bytes per pixel
int rgb_stride, // bytes per scanline
WebPPicture* const picture) {
const WebPEncCSP uv_csp = picture->colorspace & WEBP_CSP_UV_MASK;
int x, y;
const int width = picture->width;
const int height = picture->height;
const int has_alpha = CheckNonOpaque(a_ptr, width, height, step, rgb_stride);
picture->colorspace = uv_csp;
picture->use_argb_input = 0;
if (has_alpha) {
picture->colorspace |= WEBP_CSP_ALPHA_BIT;
}
if (!WebPPictureAlloc(picture)) return 0;
// Import luma plane
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const int offset = step * x + y * rgb_stride;
picture->y[x + y * picture->y_stride] =
rgb_to_y(r_ptr[offset], g_ptr[offset], b_ptr[offset]);
}
}
// Downsample U/V plane
if (uv_csp != WEBP_YUV400) {
for (y = 0; y < (height >> 1); ++y) {
for (x = 0; x < (width >> 1); ++x) {
RGB_TO_UV(x, y, SUM4);
}
if (picture->width & 1) {
RGB_TO_UV(x, y, SUM2V);
}
}
if (height & 1) {
for (x = 0; x < (width >> 1); ++x) {
RGB_TO_UV(x, y, SUM2H);
}
if (width & 1) {
RGB_TO_UV(x, y, SUM1);
}
}
#ifdef WEBP_EXPERIMENTAL_FEATURES
// Store original U/V samples too
if (uv_csp == WEBP_YUV422) {
for (y = 0; y < height; ++y) {
for (x = 0; x < (width >> 1); ++x) {
RGB_TO_UV0(2 * x, x, y, SUM2H);
}
if (width & 1) {
RGB_TO_UV0(2 * x, x, y, SUM1);
}
}
} else if (uv_csp == WEBP_YUV444) {
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
RGB_TO_UV0(x, x, y, SUM1);
}
}
}
#endif
} else {
MakeGray(picture);
}
if (has_alpha) {
assert(step >= 4);
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
picture->a[x + y * picture->a_stride] =
a_ptr[step * x + y * rgb_stride];
}
}
}
return 1;
}
static int Import(WebPPicture* const picture,
const uint8_t* const rgb, int rgb_stride,
int step, int swap_rb, int import_alpha) {
const WebPEncCSP uv_csp = picture->colorspace & WEBP_CSP_UV_MASK;
int x, y;
const uint8_t* const r_ptr = rgb + (swap_rb ? 2 : 0);
const uint8_t* const g_ptr = rgb + 1;
const uint8_t* const b_ptr = rgb + (swap_rb ? 0 : 2);
const uint8_t* const a_ptr = import_alpha ? rgb + 3 : NULL;
const int width = picture->width;
const int height = picture->height;
if (!picture->use_argb_input) {
return ImportYUVAFromRGBA(r_ptr, g_ptr, b_ptr, a_ptr, step, rgb_stride,
picture);
}
if (import_alpha) {
picture->colorspace |= WEBP_CSP_ALPHA_BIT;
} else {
@ -552,94 +715,30 @@ static int Import(WebPPicture* const picture,
}
if (!WebPPictureAlloc(picture)) return 0;
if (!picture->use_argb_input) {
// Import luma plane
if (!import_alpha) {
int x, y;
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const int offset = step * x + y * rgb_stride;
picture->y[x + y * picture->y_stride] =
rgb_to_y(r_ptr[offset], g_ptr[offset], b_ptr[offset]);
}
}
// Downsample U/V plane
if (uv_csp != WEBP_YUV400) {
for (y = 0; y < (height >> 1); ++y) {
for (x = 0; x < (width >> 1); ++x) {
RGB_TO_UV(x, y, SUM4);
}
if (picture->width & 1) {
RGB_TO_UV(x, y, SUM2V);
}
}
if (height & 1) {
for (x = 0; x < (width >> 1); ++x) {
RGB_TO_UV(x, y, SUM2H);
}
if (width & 1) {
RGB_TO_UV(x, y, SUM1);
}
}
#ifdef WEBP_EXPERIMENTAL_FEATURES
// Store original U/V samples too
if (uv_csp == WEBP_YUV422) {
for (y = 0; y < height; ++y) {
for (x = 0; x < (width >> 1); ++x) {
RGB_TO_UV0(2 * x, x, y, SUM2H);
}
if (width & 1) {
RGB_TO_UV0(2 * x, x, y, SUM1);
}
}
} else if (uv_csp == WEBP_YUV444) {
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
RGB_TO_UV0(x, x, y, SUM1);
}
}
}
#endif
} else {
MakeGray(picture);
}
if (import_alpha) {
const uint8_t* const a_ptr = rgb + 3;
assert(step >= 4);
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
picture->a[x + y * picture->a_stride] =
a_ptr[step * x + y * rgb_stride];
}
const uint32_t argb =
0xff000000u |
(r_ptr[offset] << 16) |
(g_ptr[offset] << 8) |
(b_ptr[offset]);
picture->argb[x + y * picture->argb_stride] = argb;
}
}
} else {
if (!import_alpha) {
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const int offset = step * x + y * rgb_stride;
const uint32_t argb =
0xff000000 |
(r_ptr[offset] << 16) |
(g_ptr[offset] << 8) |
(b_ptr[offset]);
picture->argb[x + y * picture->argb_stride] = argb;
}
}
} else {
const uint8_t* const a_ptr = rgb + 3;
assert(step >= 4);
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const int offset = step * x + y * rgb_stride;
const uint32_t argb =
(a_ptr[offset] << 24) |
(r_ptr[offset] << 16) |
(g_ptr[offset] << 8) |
(b_ptr[offset]);
picture->argb[x + y * picture->argb_stride] = argb;
}
int x, y;
assert(step >= 4);
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
const int offset = step * x + y * rgb_stride;
const uint32_t argb = (a_ptr[offset] << 24) |
(r_ptr[offset] << 16) |
(g_ptr[offset] << 8) |
(b_ptr[offset]);
picture->argb[x + y * picture->argb_stride] = argb;
}
}
}
@ -681,6 +780,96 @@ int WebPPictureImportBGRX(WebPPicture* const picture,
return Import(picture, rgba, rgba_stride, 4, 1, 0);
}
//------------------------------------------------------------------------------
// Automatic YUV <-> ARGB conversions.
int WebPPictureYUVAToARGB(WebPPicture* const picture) {
if (picture == NULL) return 0;
if (picture->memory_ == NULL || picture->y == NULL ||
picture->u == NULL || picture->v == NULL) {
return WebPEncodingSetError(picture, VP8_ENC_ERROR_NULL_PARAMETER);
}
if ((picture->colorspace & WEBP_CSP_ALPHA_BIT) && picture->a == NULL) {
return WebPEncodingSetError(picture, VP8_ENC_ERROR_NULL_PARAMETER);
}
if ((picture->colorspace & WEBP_CSP_UV_MASK) != WEBP_YUV420) {
return WebPEncodingSetError(picture, VP8_ENC_ERROR_INVALID_CONFIGURATION);
}
// Allocate a new argb buffer (discarding the previous one).
if (!PictureAllocARGB(picture)) return 0;
// Convert
{
int y;
const int width = picture->width;
const int height = picture->height;
const int argb_stride = 4 * picture->argb_stride;
uint8_t* dst = (uint8_t*)picture->argb;
const uint8_t *cur_u = picture->u, *cur_v = picture->v, *cur_y = picture->y;
WebPUpsampleLinePairFunc upsample = WebPGetLinePairConverter(ALPHA_IS_LAST);
// First row, with replicated top samples.
upsample(NULL, cur_y, cur_u, cur_v, cur_u, cur_v, NULL, dst, width);
cur_y += picture->y_stride;
dst += argb_stride;
// Center rows.
for (y = 1; y + 1 < height; y += 2) {
const uint8_t* const top_u = cur_u;
const uint8_t* const top_v = cur_v;
cur_u += picture->uv_stride;
cur_v += picture->uv_stride;
upsample(cur_y, cur_y + picture->y_stride, top_u, top_v, cur_u, cur_v,
dst, dst + argb_stride, width);
cur_y += 2 * picture->y_stride;
dst += 2 * argb_stride;
}
// Last row (if needed), with replicated bottom samples.
if (height > 1 && !(height & 1)) {
upsample(cur_y, NULL, cur_u, cur_v, cur_u, cur_v, dst, NULL, width);
}
// Insert alpha values if needed, in replacement for the default 0xff ones.
if (picture->colorspace & WEBP_CSP_ALPHA_BIT) {
for (y = 0; y < height; ++y) {
uint32_t* const dst = picture->argb + y * picture->argb_stride;
const uint8_t* const src = picture->a + y * picture->a_stride;
int x;
for (x = 0; x < width; ++x) {
dst[x] = (dst[x] & 0x00ffffffu) | (src[x] << 24);
}
}
}
}
return 1;
}
int WebPPictureARGBToYUVA(WebPPicture* const picture, WebPEncCSP colorspace) {
if (picture == NULL) return 0;
if (picture->argb == NULL) {
return WebPEncodingSetError(picture, VP8_ENC_ERROR_NULL_PARAMETER);
} else {
const uint8_t* const argb = (const uint8_t*)picture->argb;
const uint8_t* const r = ALPHA_IS_LAST ? argb + 2 : argb + 1;
const uint8_t* const g = ALPHA_IS_LAST ? argb + 1 : argb + 2;
const uint8_t* const b = ALPHA_IS_LAST ? argb + 0 : argb + 3;
const uint8_t* const a = ALPHA_IS_LAST ? argb + 3 : argb + 0;
// We work on a tmp copy of 'picture', because ImportYUVAFromRGBA()
// would be calling WebPPictureFree(picture) otherwise.
WebPPicture tmp = *picture;
PictureResetARGB(&tmp); // reset ARGB buffer so that it's not free()'d.
tmp.use_argb_input = 0;
tmp.colorspace = colorspace & WEBP_CSP_UV_MASK;
if (!ImportYUVAFromRGBA(r, g, b, a, 4, 4 * picture->argb_stride, &tmp)) {
return WebPEncodingSetError(picture, VP8_ENC_ERROR_OUT_OF_MEMORY);
}
// Copy back the YUV specs into 'picture'.
tmp.argb = picture->argb;
tmp.argb_stride = picture->argb_stride;
tmp.memory_argb_ = picture->memory_argb_;
*picture = tmp;
}
return 1;
}
//------------------------------------------------------------------------------
// Helper: clean up fully transparent area to help compressibility.
@ -746,32 +935,6 @@ void WebPCleanupTransparentArea(WebPPicture* const pic) {
#undef SIZE
#undef SIZE2
// Checking for the presence of non-opaque alpha.
int WebPPictureHasTransparency(const WebPPicture* const pic) {
if (pic == NULL) return 0;
if (!pic->use_argb_input) {
int x, y;
const uint8_t* alpha = pic->a;
if (alpha == NULL) return 0;
for (y = 0; y < pic->height; ++y) {
for (x = 0; x < pic->width; ++x) {
if (alpha[x] != 0xff) return 1;
}
alpha += pic->a_stride;
}
} else {
int x, y;
const uint32_t* argb = pic->argb;
if (argb == NULL) return 1;
for (y = 0; y < pic->height; ++y) {
for (x = 0; x < pic->width; ++x) {
if (argb[x] < 0xff000000) return 1; // test any alpha values != 0xff
}
argb += pic->argb_stride;
}
}
return 0;
}
//------------------------------------------------------------------------------
// Distortion
@ -794,6 +957,11 @@ int WebPPictureDistortion(const WebPPicture* const pic1,
result == NULL) {
return 0;
}
// TODO(skal): provide distortion for ARGB too.
if (pic1->use_argb_input == 1 ||
pic1->use_argb_input != pic2->use_argb_input) {
return 0;
}
has_alpha = !!(pic1->colorspace & WEBP_CSP_ALPHA_BIT);
if (has_alpha != !!(pic2->colorspace & WEBP_CSP_ALPHA_BIT) ||

9
src/enc/webpenc.c
View File

@ -345,8 +345,13 @@ int WebPEncode(const WebPConfig* const config, WebPPicture* const pic) {
if (!config->lossless) {
VP8Encoder* enc = NULL;
if (pic->y == NULL || pic->u == NULL || pic->v == NULL)
return WebPEncodingSetError(pic, VP8_ENC_ERROR_NULL_PARAMETER);
if (pic->y == NULL || pic->u == NULL || pic->v == NULL) {
if (pic->argb != NULL) {
if (!WebPPictureARGBToYUVA(pic, WEBP_YUV420)) return 0;
} else {
return WebPEncodingSetError(pic, VP8_ENC_ERROR_NULL_PARAMETER);
}
}
enc = InitVP8Encoder(config, pic);
if (enc == NULL) return 0; // pic->error is already set.

29
src/webp/encode.h
View File

@ -349,15 +349,31 @@ WEBP_EXTERN(int) WebPPictureImportBGRA(
WEBP_EXTERN(int) WebPPictureImportBGRX(
WebPPicture* const picture, const uint8_t* const bgrx, int bgrx_stride);
// Converts picture->argb data to the YUVA format specified by 'colorspace'.
// Upon return, picture->use_argb_input is set to false. The presence of
// real non-opaque transparent values is detected, and 'colorspace' will be
// adjusted accordingly. Note that this method is lossy.
// Returns false in case of error.
WEBP_EXTERN(int) WebPPictureARGBToYUVA(WebPPicture* const picture,
WebPEncCSP colorspace);
// Converts picture->yuv to picture->argb and sets picture->use_argb_input
// to true. The input format must be YUV_420 or YUV_420A.
// Note that the use of this method is discouraged if one has access to the
// raw ARGB samples, since using YUV420 is comparatively lossy. Also, the
// conversion from YUV420 to ARGB incurs a small loss too.
// Returns false in case of error.
WEBP_EXTERN(int) WebPPictureYUVAToARGB(WebPPicture* const picture);
// Helper function: given a width x height plane of YUV(A) samples
// (with stride 'stride'), clean-up the YUV samples under fully transparent
// area, to help compressibility (no guarantee, though).
WEBP_EXTERN(void) WebPCleanupTransparentArea(WebPPicture* const picture);
// Scan the picture 'pic' for the presence of non fully opaque alpha values.
// Scan the picture 'picture' for the presence of non fully opaque alpha values.
// Returns true in such case. Otherwise returns false (indicating that the
// alpha plane can be ignored altogether e.g.).
WEBP_EXTERN(int) WebPPictureHasTransparency(const WebPPicture* const pic);
WEBP_EXTERN(int) WebPPictureHasTransparency(const WebPPicture* const picture);
//------------------------------------------------------------------------------
// Main call
@ -367,8 +383,13 @@ WEBP_EXTERN(int) WebPPictureHasTransparency(const WebPPicture* const pic);
// and the 'config' object must be a valid one.
// Returns false in case of error, true otherwise.
// In case of error, picture->error_code is updated accordingly.
WEBP_EXTERN(int) WebPEncode(
const WebPConfig* const config, WebPPicture* const picture);
// 'picture' can hold the source samples in both YUV(A) or ARGB input, depending
// on the value of 'picture->use_argb_input'. It is highly recommended to
// use the former for lossy encoding, and the latter for lossless encoding
// (when config.lossless is true). Automatic conversion from one format to
// another is provided but they both incur some loss.
WEBP_EXTERN(int) WebPEncode(const WebPConfig* const config,
WebPPicture* const picture);
//------------------------------------------------------------------------------