dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2025-07-19 23:39:58 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

add incremental decoding

Browse Source 
The object WebPIDecoder is available to store the
decoding state. The flow is typically:

   WebPIDecoder* const idec = WebPINew(mode);
   while (has_more_data) {
     // ... (get additional data)
     status = WebPIAppend(idec, new_data, new_data_size);
     if (status != VP8_STATUS_SUSPENDED ||
       break;
     }

     // The above call decodes the current available buffer.
     // Part of the image can now be refreshed by calling to
     // WebPIDecGetRGB()/WebPIDecGetYUV() etc.
   }
   WebPIDelete(idec);

Doing so, one can try and decode new macroblocks everytime fresh
bytes are available.
There's two operating modes: either appending fresh bytes, or
updating the whole buffer with additional data in the end.
The latter requires less memcpy()'s

main patch by Somnath Banerjee (somnath at google.com)

Change-Id: Ie81cbd0b50f175743af06b1f964de838b9a10a4a
This commit is contained in:
Pascal Massimino
2011-03-23 18:03:53 -07:00
parent 1f28832834
commit 8bf76fe0c8
10 changed files with 748 additions and 79 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
src/dec/webpi.h
View File

@ -18,20 +18,20 @@ extern "C" {
#include "webp/decode_vp8.h"
typedef enum { MODE_RGB = 0, MODE_RGBA = 1,
MODE_BGR = 2, MODE_BGRA = 3,
MODE_YUV = 4 } WEBP_CSP_MODE;
// Decoding output parameters.
// Decoding output parameters.
typedef struct {
uint8_t* output; // rgb(a) or luma
uint8_t *u, *v;
uint8_t *top_y, *top_u, *top_v;
uint8_t *u, *v; // chroma u/v
uint8_t *top_y, *top_u, *top_v; // cache for the fancy upscaler
int stride; // rgb(a) stride or luma stride
int u_stride;
int v_stride;
WEBP_CSP_MODE mode;
int u_stride; // chroma-u stride
int v_stride; // chroma-v stride
WEBP_CSP_MODE mode; // rgb(a) or yuv
int last_y; // coordinate of the line that was last output
int output_size; // size of 'output' buffer
int output_u_size; // size of 'u' buffer
int output_v_size; // size of 'v' buffer
int external_buffer; // If true, the output buffers are externally owned
} WebPDecParams;
// If a RIFF container is detected, validate it and skip over it. Returns
@ -50,8 +50,7 @@ int WebPInitDecParams(const uint8_t* data, uint32_t data_size, int* width,
// Verifies various size configurations (e.g stride >= width, specified
// output size <= stride * height etc.). Returns 0 if checks fail.
int WebPCheckDecParams(const VP8Io* io, const WebPDecParams* params,
int output_size, int output_u_size, int output_v_size);
int WebPCheckDecParams(const VP8Io* io, const WebPDecParams* params);
// Deallocate memory allocated by WebPInitDecParams() and reset the
// WebPDecParams object.