Function pixThresholdOn8bpp

deps/leptonica/src/grayquant.c:1631–1683

----------------------------------------------------------------------* * Simple (pixelwise) thresholding on 8 bpp with optional colormap * *----------------------------------------------------------------------*/ ! * \brief pixThresholdOn8bpp() * * \param[in] pixs 8 bpp, can have colormap * \param[in] nlevels equally spaced; must be between 2 and 256 * \param[in] cmapflag 1

 * </pre>
 */
PIX *
pixThresholdOn8bpp(PIX     *pixs,
                   l_int32  nlevels,
                   l_int32  cmapflag)
{
l_int32   *qtab;  /* quantization table */
l_int32    i, j, w, h, wpld, val, newval;
l_uint32  *datad, *lined;
PIX       *pixd;
PIXCMAP   *cmap;

    PROCNAME("pixThresholdOn8bpp");

    if (!pixs)
        return (PIX *)ERROR_PTR("pixs not defined", procName, NULL);
    if (pixGetDepth(pixs) != 8)
        return (PIX *)ERROR_PTR("pixs not 8 bpp", procName, NULL);
    if (nlevels < 2 || nlevels > 256)
        return (PIX *)ERROR_PTR("nlevels not in [2,...,256]", procName, NULL);

        /* Get a new pixd; if there is a colormap in the src, remove it */
    if (pixGetColormap(pixs))
        pixd = pixRemoveColormap(pixs, REMOVE_CMAP_TO_GRAYSCALE);
    else
        pixd = pixCopy(NULL, pixs);

    if (cmapflag) {   /* hold out (256 - nlevels) cmap entries */
        cmap = pixcmapCreateLinear(8, nlevels);
        pixSetColormap(pixd, cmap);
    }

    if (cmapflag)
        qtab = makeGrayQuantIndexTable(nlevels);
    else
        qtab = makeGrayQuantTargetTable(nlevels, 8);

    pixGetDimensions(pixd, &w, &h, NULL);
    pixCopyResolution(pixd, pixs);
    pixCopyInputFormat(pixd, pixs);
    datad = pixGetData(pixd);
    wpld = pixGetWpl(pixd);
    for (i = 0; i < h; i++) {
        lined = datad + i * wpld;
        for (j = 0; j < w; j++) {
            val = GET_DATA_BYTE(lined, j);
            newval = qtab[val];
            SET_DATA_BYTE(lined, j, newval);
        }
    }

    LEPT_FREE(qtab);
    return pixd;
}


/*----------------------------------------------------------------------*