GUAC-236: Do not use features specific to libjpeg-turbo. Ensure compatibility with libjpeg.

This commit is contained in:
Michael Jumper 2016-03-16 11:56:04 -07:00
parent a1822c5a2c
commit fd430e8b69

View File

@ -32,6 +32,58 @@
#include <stdlib.h> #include <stdlib.h>
/**
* Translates libjpeg's 24-bit RGB format into Cairo's 32-bit ARGB32 / RGB24
* format. The red, green, and blue components from the libjpeg pixel are
* copied verbatim, while the extra high byte used within Cairo is set to 0xFF.
*
* @param src
* A pointer to the first byte of the 24-bit RGB pixel within a libjpeg
* scanline buffer.
*
* @return
* A 32-bit Cairo ARGB32 / RGB24 pixel value equivalent to the libjpeg
* pixel at the given pointer.
*/
static uint32_t guacenc_jpeg_translate_rgb(const unsigned char* src) {
/* Pull components from source */
int r = *(src++);
int g = *(src++);
int b = *(src++);
/* Translate to 32-bit integer compatible with Cairo */
return 0xFF000000 | (r << 16) | (g << 8) | b;
}
/**
* Copies the data from a libjpeg scanline buffer into a row of image data
* within a Cairo surface, translating each pixel as necessary.
*
* @param dst
* The destination buffer into which the scanline should be copied.
*
* @param src
* The libjpeg scanline buffer that should be copied into the
* destination buffer.
*
* @param width
* The number of pixels available within both the scanline buffer and the
* destination buffer.
*/
static void guacenc_jpeg_copy_scanline(unsigned char* dst,
const unsigned char* src, int width) {
uint32_t* current = (uint32_t*) dst;
/* Copy all pixels from source to destination, translating for Cairo */
for (; width > 0; width--, src += 3) {
*(current++) = guacenc_jpeg_translate_rgb(src);
}
}
cairo_surface_t* guacenc_jpeg_decoder(unsigned char* data, int length) { cairo_surface_t* guacenc_jpeg_decoder(unsigned char* data, int length) {
struct jpeg_decompress_struct cinfo; struct jpeg_decompress_struct cinfo;
@ -52,13 +104,16 @@ cairo_surface_t* guacenc_jpeg_decoder(unsigned char* data, int length) {
} }
/* Begin decompression */ /* Begin decompression */
cinfo.out_color_space = JCS_EXT_BGRX; cinfo.out_color_space = JCS_RGB;
jpeg_start_decompress(&cinfo); jpeg_start_decompress(&cinfo);
/* Pull JPEG dimensions from decompressor */ /* Pull JPEG dimensions from decompressor */
int width = cinfo.output_width; int width = cinfo.output_width;
int height = cinfo.output_height; int height = cinfo.output_height;
/* Allocate sufficient buffer space for one JPEG scanline */
unsigned char* jpeg_scanline = malloc(width * 3);
/* Create blank Cairo surface (no transparency in JPEG) */ /* Create blank Cairo surface (no transparency in JPEG) */
cairo_surface_t* surface = cairo_image_surface_create(CAIRO_FORMAT_RGB24, cairo_surface_t* surface = cairo_image_surface_create(CAIRO_FORMAT_RGB24,
width, height); width, height);
@ -69,11 +124,22 @@ cairo_surface_t* guacenc_jpeg_decoder(unsigned char* data, int length) {
/* Read JPEG into surface */ /* Read JPEG into surface */
while (cinfo.output_scanline < height) { while (cinfo.output_scanline < height) {
unsigned char* buffers[1] = { row };
/* Read single scanline */
unsigned char* buffers[1] = { jpeg_scanline };
jpeg_read_scanlines(&cinfo, buffers, 1); jpeg_read_scanlines(&cinfo, buffers, 1);
/* Copy scanline to Cairo surface */
guacenc_jpeg_copy_scanline(row, jpeg_scanline, width);
/* Advance to next row of Cairo surface */
row += stride; row += stride;
} }
/* Scanline buffer is no longer needed */
free(jpeg_scanline);
/* End decompression */ /* End decompression */
jpeg_finish_decompress(&cinfo); jpeg_finish_decompress(&cinfo);