Function pixThresholdTo4bpp

deps/leptonica/src/grayquant.c:1514–1563

----------------------------------------------------------------------* * Simple (pixelwise) thresholding to 4 bpp * *----------------------------------------------------------------------*/ ! * \brief pixThresholdTo4bpp() * * \param[in] pixs 8 bpp, can have colormap * \param[in] nlevels equally spaced; must be between 2 and 16 * \param[in] cmapflag 1

 * </pre>
 */
PIX *
pixThresholdTo4bpp(PIX     *pixs,
                   l_int32  nlevels,
                   l_int32  cmapflag)
{
l_int32   *qtab;
l_int32    w, h, d, wplt, wpld;
l_uint32  *datat, *datad;
PIX       *pixt, *pixd;
PIXCMAP   *cmap;

    PROCNAME("pixThresholdTo4bpp");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    pixGetDimensions(pixs, &w, &h, &d);
    if (d != 8)
        return (PIX *)ERROR_PTR("pixs not 8 bpp", procName, NULL);
    if (nlevels < 2 || nlevels > 16)
        return (PIX *)ERROR_PTR("nlevels not in [2,...,16]", procName, NULL);

    if ((pixd = pixCreate(w, h, 4)) == NULL)
        return (PIX *)ERROR_PTR("pixd not made", procName, NULL);
    pixCopyResolution(pixd, pixs);
    pixCopyInputFormat(pixd, pixs);
    datad = pixGetData(pixd);
    wpld = pixGetWpl(pixd);

    if (cmapflag) {   /* hold out (16 - nlevels) cmap entries */
        cmap = pixcmapCreateLinear(4, nlevels);
        pixSetColormap(pixd, cmap);
    }

        /* If there is a colormap in the src, remove it */
    pixt = pixRemoveColormap(pixs, REMOVE_CMAP_TO_GRAYSCALE);
    datat = pixGetData(pixt);
    wplt = pixGetWpl(pixt);

        /* Make the appropriate table */
    if (cmapflag)
        qtab = makeGrayQuantIndexTable(nlevels);
    else
        qtab = makeGrayQuantTargetTable(16, 4);

    thresholdTo4bppLow(datad, h, wpld, datat, wplt, qtab);

    LEPT_FREE(qtab);
    pixDestroy(&pixt);
    return pixd;
}


/*!