cairo_jpg

Introduction

This is an implementation of functions to import and export Cairo surfaces from and to JPEG files. It uses the same function prototypes as Cairo's PNG support.

Description

The implementation is done on top of the Cairo API. It does not access Cairo-internal functions. For compression and decompression a JPEG library is used. It compiles against libjpeg-turbo or the original libjpeg.

The following prototypes are implemented. Their functionality is equal to the PNG functions of Cairo with the advance that there are memory-buffer-based functions as well.

cairo_status_t cairo_image_surface_write_to_jpeg_mem(cairo_surface_t *sfc, unsigned char **data, size_t *len, int quality);
cairo_status_t cairo_image_surface_write_to_jpeg_stream(cairo_surface_t *sfc, cairo_write_func_t write_func, void *closure, int quality);
cairo_status_t cairo_image_surface_write_to_jpeg(cairo_surface_t *sfc, const char *filename, int quality);
cairo_surface_t *cairo_image_surface_create_from_jpeg_mem(void *data, size_t len);
cairo_surface_t *cairo_image_surface_create_from_jpeg_stream(cairo_read_func_t read_func, void *closure);
cairo_surface_t *cairo_image_surface_create_from_jpeg(const char *filename);

To compile this code you need to have installed the packages libcairo2-dev and libjpeg-dev. Compile with the following command to create an object file linkable to your code:

gcc -Wall -c `pkg-config cairo libjpeg --cflags --libs` cairo_jpg.c

Please have a look at the comments within the source files for further details. Don't hesitate to contact me at bf@abenteuerland.at.

Testing

There is a main() function implemented which serves as demonstrational purpose and for testing. To compile with the main() function run the following statement:

gcc -Wall -o cairo_jpg -DCAIRO_JPEG_MAIN `pkg-config cairo libjpeg --cflags --libs` cairo_jpg.c