Release Notes

Open Source Used In AsyncOS 8.8 for Cisco Web Security Appliances

...

if ((outfile = fopen(filename, "wb")) == NULL) {

 fprintf(stderr, "can't open %s\n", filename);

 exit(1);

}

jpeg_stdio_dest(&cinfo, outfile);

where the last line invokes the standard destination module.

WARNING: it is critical that the binary compressed data be delivered to the

output file unchanged. On non-Unix systems the stdio library may perform

newline translation or otherwise corrupt binary data. To suppress this

behavior, you may need to use a "b" option to fopen (as shown above), or use

setmode() or another routine to put the stdio stream in binary mode. See

cjpeg.c and djpeg.c for code that has been found to work on many systems.

You can select the data destination after setting other parameters (step 3),

if that's more convenient. You may not change the destination between

calling jpeg_start_compress() and jpeg_finish_compress().

3. Set parameters for compression, including image size & colorspace.

You must supply information about the source image by setting the following

fields in the JPEG object (cinfo structure):

image_widthWidth of image, in pixels

image_heightHeight of image, in pixels

input_componentsNumber of color channels (samples per pixel)

in_color_spaceColor space of source image

The image dimensions are, hopefully, obvious. JPEG supports image dimensions

of 1 to 64K pixels in either direction. The input color space is typically

RGB or grayscale, and input_components is 3 or 1 accordingly. (See "Special

color spaces", later, for more info.) The in_color_space field must be

assigned one of the J_COLOR_SPACE enum constants, typically JCS_RGB or

JCS_GRAYSCALE.

JPEG has a large number of compression parameters that determine how the

image is encoded. Most applications don't need or want to know about all

these parameters. You can set all the parameters to reasonable defaults by

calling jpeg_set_defaults(); then, if there are particular values you want

to change, you can do so after that. The "Compression parameter selection"

section tells about all the parameters.

You must set in_color_space correctly before calling jpeg_set_defaults(),

because the defaults depend on the source image colorspace. However the

other three source image parameters need not be valid until you call