once i needed that for resizing all images in a directory to a specified delta. since JUCE don’t have anything about image saving (only loading, and it’s a pity tho cause sometimes i use manipulate images with it) i finally coded this. nothing special just a callable function to save a Image to file:
[code]bool juce_saveJPEGImageToFile(const Image& img, const String& imageFileName, int quality)
{
/* This struct contains the JPEG compression parameters and pointers to
* working space (which is allocated as needed by the JPEG library).
* It is possible to have several such structures, representing multiple
* compression/decompression processes, in existence at once. We refer
* to any one struct (and its associated working data) as a “JPEG object”.
/
struct jpeg_compress_struct cinfo;
/ This struct represents a JPEG error handler. It is declared separately
* because applications often want to supply a specialized error handler
* (see the second half of this file for an example). But here we just
* take the easy way out and use the standard error handler, which will
* print a message on stderr and call exit() if compression fails.
* Note that this struct must live as long as the main JPEG parameter
* struct, to avoid dangling-pointer problems.
/
struct jpeg_error_mgr jerr;
/ More stuff /
FILE * outfile; / target file /
int row_stride; / physical row width in image buffer /
JSAMPARRAY buffer; / Output row buffer */
/* Step 1: allocate and initialize JPEG compression object */
/* We have to set up the error handler first, in case the initialization
* step fails. (Unlikely, but it could happen if you are out of memory.)
* This routine fills in the contents of struct jerr, and returns jerr’s
* address which we place into the link field in cinfo.
/
cinfo.err = jpeg_std_error(&jerr);
/ Now we can initialize the JPEG compression object. */
jpeg_create_compress(&cinfo);
/* Step 2: specify data destination (eg, a file) /
/ Note: steps 2 and 3 can be done in either order. */
/* Here we use the library-supplied code to send compressed data to a
* stdio stream. You can also write your own code to do something else.
* VERY IMPORTANT: use “b” option to fopen() if you are on a machine that
* requires it in order to write binary files.
*/
if ((outfile = fopen((const char *)imageFileName, “wb”)) == NULL) {
return false;
}
jpeg_stdio_dest(&cinfo, outfile);
/* Step 3: set parameters for compression */
/* First we supply a description of the input image.
* Four fields of the cinfo struct must be filled in:
/
cinfo.image_width = img.getWidth(); // image width and height, in pixels
cinfo.image_height = img.getHeight();
cinfo.input_components = 3; // # of color components per pixel
cinfo.in_color_space = JCS_RGB; / colorspace of input image */
/* Now use the library’s routine to set default compression parameters.
* (You must set at least cinfo.in_color_space before calling this,
* since the defaults depend on the source color space.)
/
jpeg_set_defaults(&cinfo);
/ Now you can set any non-default parameters you wish to.
* Here we just illustrate the use of quality (quantization table) scaling:
/
jpeg_set_quality(&cinfo, quality, TRUE / limit to baseline-JPEG values */);
/* Step 4: Start compressor */
/* TRUE ensures that we will write a complete interchange-JPEG file.
* Pass TRUE unless you are very sure of what you’re doing.
*/
jpeg_start_compress(&cinfo, TRUE);
/* Step 5: while (scan lines remain to be written) /
/ jpeg_write_scanlines(…); */
/* Here we use the library’s state variable cinfo.next_scanline as the
* loop counter, so that we don’t have to keep track ourselves.
* To keep things simple, we pass one scanline per call; you can pass
* more if you wish, though.
/
row_stride = cinfo.image_widthcinfo.input_components; /* samples per row in image_buffer */
buffer = (*cinfo.mem->alloc_sarray)
((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
int numRow = 0; // cinfo.image_height -1;
while (cinfo.next_scanline < cinfo.image_height)
{
unsigned char* pix = img.getPixelPointer(0,numRow++);
int k = 0;
for (int i=0; i<img.getWidth(); i++, k+=3)
{
if (img.hasAlphaChannel() )
pix++;
buffer[0][k+2] = *pix++;
buffer[0][k+1] = *pix++;
buffer[0][k+0] = *pix++;
}
(void) jpeg_write_scanlines(&cinfo, buffer, 1);
}
/* Step 6: Finish compression */
jpeg_finish_compress(&cinfo);
/* After finish_compress, we can close the output file. */
fclose(outfile);
/* Step 7: release JPEG compression object /
/ This is an important step since it will release a good deal of memory. */
jpeg_destroy_compress(&cinfo);
/* And we’re done! */
return true;
} [/code]
hope someone is finding this useful. i’ll implement the gif and png ones (and use File or Stream instead of the String parameter)
lou
