rt_band_reclass_exact()

rt_band rt_band_reclass_exact	(	rt_band	srcband,
		rt_reclassmap	map,
		uint32_t	hasnodata,
		double	nodataval
	)

Returns new band with values reclassified.

Parameters

srcband	: the band who's values will be reclassified
map	: rt_reclassmap with src->dst mappings
hasnodata	: indicates if the user is supplying a nodata
nodataval	: user supplied nodata value for the new band

Returns

a new rt_band or NULL on error

Definition at line 288 of file rt_mapalgebra.c.

  {
        rt_band band = NULL;
        uint32_t width = 0;
        uint32_t height = 0;
        int numval = 0;
        int memsize = 0;
        void *mem = NULL;
        uint32_t src_hasnodata = 0;
        rt_pixtype pixtype;
 
        assert(NULL != srcband);
        assert(NULL != map);
 
        /* Validate that the map has consistent array lengths */
        if (map->count == 0)
                rterror("%s: reclassification map must contain at least one class pair", __func__);
 
        /* Need a nodataval from somewhere */
        src_hasnodata = rt_band_get_hasnodata_flag(srcband);
        if (!(src_hasnodata || hasnodata))
                rterror("%s: source band missing nodata value and nodata value not supplied", __func__);
 
        /*
        * Use the nodata value of the input in the case where user
        * does not supply a nodataval
        */
        if (!hasnodata && src_hasnodata) {
                rt_band_get_nodata(srcband, &nodataval);
                hasnodata = src_hasnodata;
        }
 
        /* size of memory block to allocate */
        width = rt_band_get_width(srcband);
        height = rt_band_get_height(srcband);
        numval = width * height;
        pixtype = map->dsttype;
        memsize = rt_pixtype_size(pixtype) * numval;
        mem = (int *) rtalloc(memsize);
        if (!mem)
                rterror("%s: Could not allocate memory for band", __func__);
 
        band = rt_band_new_inline(width, height, pixtype, hasnodata, nodataval, mem);
    if (! band) {
        rterror("%s: Could not add band to raster. Aborting", __func__);
        rtdealloc(mem);
        return NULL;
    }
        rt_band_set_ownsdata_flag(band, 1); /* we own this data */
 
        /*
         * apply nodata as baseline value and then only
         * map in values that match our map
         */
        rt_band_init_value(band, nodataval);
 
        /*
         * Put the rt_classpairs in order of source value
         * so we can bsearch them
         */
        qsort(map->pairs, map->count, sizeof(struct rt_classpair_t), rt_classpair_cmp);
 
        for (uint32_t x = 0; x < width; x++) {
                for (uint32_t y = 0; y < height; y++) {
                        int isnodata;
                        double nv = nodataval;
                        struct rt_classpair_t query = {0.0, 0.0};
                        struct rt_classpair_t *rslt;
 
                        /* get pixel, skip on error */
                        if (rt_band_get_pixel(srcband, x, y, &query.src, &isnodata) != ES_NONE)
                                continue;
 
                        /* output was already initialized to nodataval */
                        if (isnodata)
                                continue;
                        /*
                         * Look for pixel value in map.
                         * If not in map, skip, leaving the nodata value in place.
                         * Otherwise continue and replace with new value
                         */
                        rslt = bsearch(&query, map->pairs, map->count, sizeof(struct rt_classpair_t), rt_classpair_cmp);
                        if (!rslt)
                                continue;
                        else
                                nv = rslt->dst;
 
                        /* round the new value for integer pixel types */
                        nv = rt_band_reclass_round_integer(pixtype, nv);
 
                        if (rt_band_set_pixel(band, x, y, nv, NULL) != ES_NONE) {
                                rterror("%s: Could not assign value to new band", __func__);
                                rt_band_destroy(band);
                                rtdealloc(mem);
                                return NULL;
                        }
                }
        }
 
        return band;
}

References ovdump::band, rt_reclassmap_t::count, rt_classpair_t::dst, rt_reclassmap_t::dsttype, ES_NONE, rt_reclassmap_t::pairs, rt_band_destroy(), rt_band_get_hasnodata_flag(), rt_band_get_height(), rt_band_get_nodata(), rt_band_get_pixel(), rt_band_get_width(), rt_band_init_value(), rt_band_new_inline(), rt_band_reclass_round_integer(), rt_band_set_ownsdata_flag(), rt_band_set_pixel(), rt_classpair_cmp(), rt_pixtype_size(), rtalloc(), rtdealloc(), rterror(), rt_classpair_t::src, pixval::x, and pixval::y.

Referenced by RASTER_reclass_exact().

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