Function rtjpeg_decode_init

libavcodec/rtjpeg.c:156–173

* \brief initialize an RTJpegContext, may be called multiple times * \param c context to initialize * \param dsp specifies the idct to use for decoding * \param width width of image, will be rounded down to the nearest multiple * of 16 for decoding * \param height height of image, will be rounded down to the nearest multiple * of 16 for decoding * \param lquant lum

 * \param cquant chroma quantization table to use
 */
void rtjpeg_decode_init(RTJpegContext *c, DSPContext *dsp,
                        int width, int height,
                        const uint32_t *lquant, const uint32_t *cquant) {
    int i;
    c->dsp = dsp;
    for (i = 0; i < 64; i++) {
        int z = ff_zigzag_direct[i];
        int p = c->dsp->idct_permutation[i];
        z = ((z << 3) | (z >> 3)) & 63; // rtjpeg uses a transposed variant

        // permute the scan and quantization tables for the chosen idct
        c->scan[i] = c->dsp->idct_permutation[z];
        c->lquant[p] = lquant[i];
        c->cquant[p] = cquant[i];
    }
    c->w = width;
    c->h = height;
}