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@@ -53,5 +53,119 @@ write_data(xel *array, xelval *) {
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return 0;
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}
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+ /* This struct contains the JPEG compression parameters and pointers to
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+ * working space (which is allocated as needed by the JPEG library).
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+ * It is possible to have several such structures, representing multiple
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+ * compression/decompression processes, in existence at once. We refer
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+ * to any one struct (and its associated working data) as a "JPEG object".
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+ */
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+ struct jpeg_compress_struct cinfo;
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+ /* This struct represents a JPEG error handler. It is declared separately
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+ * because applications often want to supply a specialized error handler
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+ * (see the second half of this file for an example). But here we just
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+ * take the easy way out and use the standard error handler, which will
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+ * print a message on stderr and call exit() if compression fails.
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+ * Note that this struct must live as long as the main JPEG parameter
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+ * struct, to avoid dangling-pointer problems.
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+ */
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+ struct jpeg_error_mgr jerr;
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+ /* More stuff */
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+ JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
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+ int row_stride; /* physical row width in image buffer */
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+
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+ /* Step 1: allocate and initialize JPEG compression object */
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+
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+ /* We have to set up the error handler first, in case the initialization
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+ * step fails. (Unlikely, but it could happen if you are out of memory.)
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+ * This routine fills in the contents of struct jerr, and returns jerr's
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+ * address which we place into the link field in cinfo.
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+ */
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+ cinfo.err = jpeg_std_error(&jerr);
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+
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+ /* Now we can initialize the JPEG compression object. */
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+ jpeg_create_compress(&cinfo);
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+
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+ /* Step 2: specify data destination (eg, a file) */
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+ /* Note: steps 2 and 3 can be done in either order. */
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+
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+ /* Here we use the library-supplied code to send compressed data to a
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+ * stdio stream. You can also write your own code to do something else.
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+ * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
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+ * requires it in order to write binary files.
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+ */
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+ jpeg_stdio_dest(&cinfo, _file);
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+
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+ /* Step 3: set parameters for compression */
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+
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+ /* First we supply a description of the input image.
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+ * Four fields of the cinfo struct must be filled in:
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+ */
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+ cinfo.image_width = _x_size; /* image width and height, in pixels */
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+ cinfo.image_height = _y_size;
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+ if (is_grayscale())
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+ cinfo.input_components = 1;
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+ else
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+ cinfo.input_components = 3;
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+ cinfo.in_color_space = JCS_RGB; /* colorspace of input image */
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+ /* Now use the library's routine to set default compression parameters.
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+ * (You must set at least cinfo.in_color_space before calling this,
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+ * since the defaults depend on the source color space.)
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+ */
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+ jpeg_set_defaults(&cinfo);
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+ /* Now you can set any non-default parameters you wish to.
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+ * Here we just illustrate the use of quality (quantization table) scaling:
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+ */
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+ jpeg_set_quality(&cinfo, jpeg_quality, TRUE /* limit to baseline-JPEG values */);
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+
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+ /* Step 4: Start compressor */
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+
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+ /* TRUE ensures that we will write a complete interchange-JPEG file.
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+ * Pass TRUE unless you are very sure of what you're doing.
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+ */
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+ jpeg_start_compress(&cinfo, TRUE);
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+
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+ /* Step 5: while (scan lines remain to be written) */
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+ /* jpeg_write_scanlines(...); */
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+
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+ /* Here we use the library's state variable cinfo.next_scanline as the
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+ * loop counter, so that we don't have to keep track ourselves.
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+ * To keep things simple, we pass one scanline per call; you can pass
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+ * more if you wish, though.
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+ */
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+ row_stride = _x_size * cinfo.input_components; /* JSAMPLEs per row in image_buffer */
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+
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+ int x = 0;
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+ JSAMPROW row = new JSAMPLE[row_stride];
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+ while (cinfo.next_scanline < cinfo.image_height) {
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+ /* jpeg_write_scanlines expects an array of pointers to scanlines.
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+ * Here the array is only one element long, but you could pass
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+ * more than one scanline at a time if that's more convenient.
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+ */
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+ for (int i = 0; i < row_stride; i += cinfo.input_components) {
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+ if (cinfo.input_components == 1) {
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+ row[i] = (JSAMPLE)(MAXJSAMPLE * PPM_GETB(array[x])/_maxval);
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+ } else {
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+ row[i] = (JSAMPLE)(MAXJSAMPLE * PPM_GETR(array[x])/_maxval);
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+ row[i+1] = (JSAMPLE)(MAXJSAMPLE * PPM_GETG(array[x])/_maxval);
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+ row[i+2] = (JSAMPLE)(MAXJSAMPLE * PPM_GETB(array[x])/_maxval);
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+ }
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+ x++;
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+ }
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+ //row_pointer[0] = & image_buffer[cinfo.next_scanline * row_stride];
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+ //(void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
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+ row_pointer[0] = row;
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+ (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
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+ }
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+ delete row;
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+
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+ /* Step 6: Finish compression */
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+
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+ jpeg_finish_compress(&cinfo);
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+
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+ /* Step 7: release JPEG compression object */
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+
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+ /* This is an important step since it will release a good deal of memory. */
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+ jpeg_destroy_compress(&cinfo);
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+
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return _y_size;
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}
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Mike Goslin