GLOBAL(void)
jinit_compress_master (j_compress_ptr cinfo)
{
long samplesperrow;
JDIMENSION jd_samplesperrow;
/* For now, precision must match compiled-in value... */
if (cinfo->data_precision != BITS_IN_JSAMPLE)
ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
/* Sanity check on image dimensions */
if (cinfo->image_height <= 0 || cinfo->image_width <= 0 ||
cinfo->input_components <= 0)
ERREXIT(cinfo, JERR_EMPTY_IMAGE);
/* Width of an input scanline must be representable as JDIMENSION. */
samplesperrow = (long) cinfo->image_width * (long) cinfo->input_components;
jd_samplesperrow = (JDIMENSION) samplesperrow;
if ((long) jd_samplesperrow != samplesperrow)
ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
/* Initialize master control (includes parameter checking/processing) */
jinit_c_master_control(cinfo, FALSE /* full compression */);
/* Preprocessing */
if (! cinfo->raw_data_in) {
jinit_color_converter(cinfo);
jinit_downsampler(cinfo);
jinit_c_prep_controller(cinfo, FALSE /* never need full buffer here */);
}
/* Forward DCT */
jinit_forward_dct(cinfo);
/* Entropy encoding: either Huffman or arithmetic coding. */
if (cinfo->arith_code)
{
jinit_arith_encoder(cinfo);
}
else {
jinit_huff_encoder(cinfo);
}
/* Need a full-image coefficient buffer in any multi-pass mode. */
jinit_c_coef_controller(cinfo,
(boolean) (cinfo->num_scans > 1 || cinfo->optimize_coding));
jinit_c_main_controller(cinfo, FALSE /* never need full buffer here */);
jinit_marker_writer(cinfo);
/* We can now tell the memory manager to allocate virtual arrays. */
(*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
/* Write the datastream header (SOI) immediately.
* Frame and scan headers are postponed till later.
* This lets application insert special markers after the SOI.
*/
(*cinfo->marker->write_file_header) (cinfo);
}
上面是JPEG中的start——compress程序，显然是先做了DCT变换，然后在接着做熵编码。那么怎么去掉DCT变换，利用自己的变换。有没有人太探讨一下。或者怎么调用熵编码程序
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