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add a decoding option to flip image vertically

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New API options: WebPDecoderOptions.flip and 'dwebp -flip ...'

it uses negative stride trick.

Also changed the decoder code to support user-supplied
buffers with negative stride, independently of the
WebPDecoderOptions.flip value.

Change-Id: I4dc0d06f0c87e51a3f3428be4fee2d6b5ad76053
This commit is contained in:
skal 2014-01-16 15:48:43 +01:00
parent 00c3c4e114
commit 5da185522b
8 changed files with 99 additions and 37 deletions
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15
README
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@ -262,19 +262,20 @@ Use following options to convert into alternate image formats:
-yuv ......... save the raw YUV samples in flat layout
Other options are:
-version .... print version number and exit.
-nofancy ..... don't use the fancy YUV420 upscaler.
-nofilter .... disable in-loop filtering.
-nodither .... disable dithering.
-version .... print version number and exit
-nofancy ..... don't use the fancy YUV420 upscaler
-nofilter .... disable in-loop filtering
-nodither .... disable dithering
-dither <d> .. dithering strength (in 0..100)
-mt .......... use multi-threading
-crop <x> <y> <w> <h> ... crop output with the given rectangle
-scale <w> <h> .......... scale the output (*after* any cropping)
-alpha ....... only save the alpha plane.
-flip ........ flip the output vertically
-alpha ....... only save the alpha plane
-incremental . use incremental decoding (useful for tests)
-h ....... this help message.
-h ....... this help message
-v ....... verbose (e.g. print encoding/decoding times)
-noasm ....... disable all assembly optimizations.
-noasm ....... disable all assembly optimizations
Visualization tool:
===================

17
examples/dwebp.c
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@ -552,20 +552,21 @@ static void Help(void) {
" -yuv ......... save the raw YUV samples in flat layout\n"
"\n"
" Other options are:\n"
" -version .... print version number and exit.\n"
" -nofancy ..... don't use the fancy YUV420 upscaler.\n"
" -nofilter .... disable in-loop filtering.\n"
" -nodither .... disable dithering.\n"
" -version .... print version number and exit\n"
" -nofancy ..... don't use the fancy YUV420 upscaler\n"
" -nofilter .... disable in-loop filtering\n"
" -nodither .... disable dithering\n"
" -dither <d> .. dithering strength (in 0..100)\n"
" -mt .......... use multi-threading\n"
" -crop <x> <y> <w> <h> ... crop output with the given rectangle\n"
" -scale <w> <h> .......... scale the output (*after* any cropping)\n"
" -alpha ....... only save the alpha plane.\n"
" -flip ........ flip the output vertically\n"
" -alpha ....... only save the alpha plane\n"
" -incremental . use incremental decoding (useful for tests)\n"
" -h ....... this help message.\n"
" -h ....... this help message\n"
" -v ....... verbose (e.g. print encoding/decoding times)\n"
#ifndef WEBP_DLL
" -noasm ....... disable all assembly optimizations.\n"
" -noasm ....... disable all assembly optimizations\n"
#endif
);
}
@ -641,6 +642,8 @@ int main(int argc, const char *argv[]) {
config.options.use_scaling = 1;
config.options.scaled_width = strtol(argv[++c], NULL, 0);
config.options.scaled_height = strtol(argv[++c], NULL, 0);
} else if (!strcmp(argv[c], "-flip")) {
config.options.flip = 1;
} else if (!strcmp(argv[c], "-v")) {
verbose = 1;
#ifndef WEBP_DLL

5
man/dwebp.1
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@ -1,5 +1,5 @@
.\" Hey, EMACS: -*- nroff -*-
.TH DWEBP 1 "December 12, 2013"
.TH DWEBP 1 "January 11, 2014"
.SH NAME
dwebp \- decompress a WebP file to an image file
.SH SYNOPSIS
@ -76,6 +76,9 @@ The top-left corner will be snapped to even coordinates if needed.
This option is meant to reduce the memory needed for cropping large images.
Note: the cropping is applied \fIbefore\fP any scaling.
.TP
.B \-flip
Flip decoded image vertically (can be useful for OpenGL textures for instance).
.TP
.BI \-scale " width height
Rescale the decoded picture to dimension \fBwidth\fP x \fBheight\fP. This
option is mostly intended to reducing the memory needed to decode large images,

62
src/dec/buffer.c
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@ -42,29 +42,34 @@ static VP8StatusCode CheckDecBuffer(const WebPDecBuffer* const buffer) {
ok = 0;
} else if (!WebPIsRGBMode(mode)) { // YUV checks
const WebPYUVABuffer* const buf = &buffer->u.YUVA;
const uint64_t y_size = (uint64_t)buf->y_stride * height;
const uint64_t u_size = (uint64_t)buf->u_stride * ((height + 1) / 2);
const uint64_t v_size = (uint64_t)buf->v_stride * ((height + 1) / 2);
const uint64_t a_size = (uint64_t)buf->a_stride * height;
const int y_stride = abs(buf->y_stride);
const int u_stride = abs(buf->u_stride);
const int v_stride = abs(buf->v_stride);
const int a_stride = abs(buf->a_stride);
const uint64_t y_size = (uint64_t)y_stride * height;
const uint64_t u_size = (uint64_t)u_stride * ((height + 1) / 2);
const uint64_t v_size = (uint64_t)v_stride * ((height + 1) / 2);
const uint64_t a_size = (uint64_t)a_stride * height;
ok &= (y_size <= buf->y_size);
ok &= (u_size <= buf->u_size);
ok &= (v_size <= buf->v_size);
ok &= (buf->y_stride >= width);
ok &= (buf->u_stride >= (width + 1) / 2);
ok &= (buf->v_stride >= (width + 1) / 2);
ok &= (y_stride >= width);
ok &= (u_stride >= (width + 1) / 2);
ok &= (v_stride >= (width + 1) / 2);
ok &= (buf->y != NULL);
ok &= (buf->u != NULL);
ok &= (buf->v != NULL);
if (mode == MODE_YUVA) {
ok &= (buf->a_stride >= width);
ok &= (a_stride >= width);
ok &= (a_size <= buf->a_size);
ok &= (buf->a != NULL);
}
} else { // RGB checks
const WebPRGBABuffer* const buf = &buffer->u.RGBA;
const uint64_t size = (uint64_t)buf->stride * height;
const int stride = abs(buf->stride);
const uint64_t size = (uint64_t)stride * height;
ok &= (size <= buf->size);
ok &= (buf->stride >= width * kModeBpp[mode]);
ok &= (stride >= width * kModeBpp[mode]);
ok &= (buf->rgba != NULL);
}
return ok ? VP8_STATUS_OK : VP8_STATUS_INVALID_PARAM;
@ -131,9 +136,35 @@ static VP8StatusCode AllocateBuffer(WebPDecBuffer* const buffer) {
return CheckDecBuffer(buffer);
}
VP8StatusCode WebPFlipBuffer(WebPDecBuffer* const buffer) {
if (buffer == NULL) {
return VP8_STATUS_INVALID_PARAM;
}
if (WebPIsRGBMode(buffer->colorspace)) {
WebPRGBABuffer* const buf = &buffer->u.RGBA;
buf->rgba += (buffer->height - 1) * buf->stride;
buf->stride = -buf->stride;
} else {
WebPYUVABuffer* const buf = &buffer->u.YUVA;
const int H = buffer->height;
buf->y += (H - 1) * buf->y_stride;
buf->y_stride = -buf->y_stride;
buf->u += ((H - 1) >> 1) * buf->u_stride;
buf->u_stride = -buf->u_stride;
buf->v += ((H - 1) >> 1) * buf->v_stride;
buf->v_stride = -buf->v_stride;
if (buf->a != NULL) {
buf->a += (H - 1) * buf->a_stride;
buf->a_stride = -buf->a_stride;
}
}
return VP8_STATUS_OK;
}
VP8StatusCode WebPAllocateDecBuffer(int w, int h,
const WebPDecoderOptions* const options,
WebPDecBuffer* const out) {
VP8StatusCode status;
if (out == NULL || w <= 0 || h <= 0) {
return VP8_STATUS_INVALID_PARAM;
}
@ -160,8 +191,15 @@ VP8StatusCode WebPAllocateDecBuffer(int w, int h,
out->width = w;
out->height = h;
// Then, allocate buffer for real
return AllocateBuffer(out);
// Then, allocate buffer for real.
status = AllocateBuffer(out);
if (status != VP8_STATUS_OK) return status;
// Use the stride trick if vertical flip is needed.
if (options != NULL && options->flip) {
status = WebPFlipBuffer(out);
}
return status;
}
//------------------------------------------------------------------------------

21
src/dec/idec.c
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@ -246,6 +246,19 @@ static int CheckMemBufferMode(MemBuffer* const mem, MemBufferMode expected) {
return 1;
}
// To be called last.
static VP8StatusCode FinishDecoding(WebPIDecoder* const idec) {
const WebPDecoderOptions* const options = idec->params_.options;
WebPDecBuffer* const output = idec->params_.output;
idec->state_ = STATE_DONE;
if (options != NULL && options->flip) {
return WebPFlipBuffer(output);
} else {
return VP8_STATUS_OK;
}
}
//------------------------------------------------------------------------------
// Macroblock-decoding contexts
@ -476,9 +489,7 @@ static VP8StatusCode DecodeRemaining(WebPIDecoder* const idec) {
return IDecError(idec, VP8_STATUS_USER_ABORT);
}
dec->ready_ = 0;
idec->state_ = STATE_DONE;
return VP8_STATUS_OK;
return FinishDecoding(idec);
}
static VP8StatusCode ErrorStatusLossless(WebPIDecoder* const idec,
@ -530,9 +541,7 @@ static VP8StatusCode DecodeVP8LData(WebPIDecoder* const idec) {
return ErrorStatusLossless(idec, dec->status_);
}
idec->state_ = STATE_DONE;
return VP8_STATUS_OK;
return FinishDecoding(idec);
}
// Main decoding loop

4
src/dec/webp.c
View File

@ -512,6 +512,10 @@ static VP8StatusCode DecodeInto(const uint8_t* const data, size_t data_size,
if (status != VP8_STATUS_OK) {
WebPFreeDecBuffer(params->output);
}
if (params->options != NULL && params->options->flip) {
status = WebPFlipBuffer(params->output);
}
return status;
}

7
src/dec/webpi.h
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@ -93,10 +93,15 @@ int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
// dimension / etc.). If *options is not NULL, also verify that the options'
// parameters are valid and apply them to the width/height dimensions of the
// output buffer. This takes cropping / scaling / rotation into account.
// Also incorporates the options->flip flag to flip the buffer parameters if
// needed.
VP8StatusCode WebPAllocateDecBuffer(int width, int height,
const WebPDecoderOptions* const options,
WebPDecBuffer* const buffer);
// Flip buffer vertically by negating the various strides.
VP8StatusCode WebPFlipBuffer(WebPDecBuffer* const buffer);
// Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
// memory (still held by 'src').
void WebPCopyDecBuffer(const WebPDecBuffer* const src,
@ -105,8 +110,6 @@ void WebPCopyDecBuffer(const WebPDecBuffer* const src,
// Copy and transfer ownership from src to dst (beware of parameter order!)
void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
//------------------------------------------------------------------------------
#ifdef __cplusplus

5
src/webp/decode.h
View File

@ -20,7 +20,7 @@
extern "C" {
#endif
#define WEBP_DECODER_ABI_VERSION 0x0203 // MAJOR(8b) + MINOR(8b)
#define WEBP_DECODER_ABI_VERSION 0x0204 // MAJOR(8b) + MINOR(8b)
// Note: forward declaring enumerations is not allowed in (strict) C and C++,
// the types are left here for reference.
@ -442,11 +442,12 @@ struct WebPDecoderOptions {
int scaled_width, scaled_height; // final resolution
int use_threads; // if true, use multi-threaded decoding
int dithering_strength; // dithering strength (0=Off, 100=full)
int flip; // flip output vertically
// Unused for now:
int force_rotation; // forced rotation (to be applied _last_)
int no_enhancement; // if true, discard enhancement layer
uint32_t pad[5]; // padding for later use
uint32_t pad[4]; // padding for later use
};
// Main object storing the configuration for advanced decoding.