pngdriver/raster.c

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/*!
   \file lib/pngdriver/raster.c
 
   \brief GRASS png display driver - draw raster
 
   (C) 2003-2014 by Per Henrik Johansen and the GRASS Development Team
 
   This program is free software under the GNU General Public License
   (>=v2). Read the file COPYING that comes with GRASS for details.
 
   \author Per Henrik Johansen (original contributor)
   \author Glynn Clements
 */
 
#include <string.h>
#include <math.h>
#include <grass/gis.h>
#include "driver.h"
#include "pngdriver.h"
 
#ifndef min
#define min(a, b) ((a) < (b) ? (a) : (b))
#endif
#ifndef max
#define max(a, b) ((a) > (b) ? (a) : (b))
#endif
 
static int *trans;
static int ncols;
static int nalloc;
static int masked;
static int src[2][2];
static int dst[2][2];
 
static double scale(double k, const int src[2], const int dst[2])
{
    return dst[0] +
           (double)(k - src[0]) * (dst[1] - dst[0]) / (src[1] - src[0]);
}
 
static int scale_fwd_y(int sy)
{
    return (int)floor(scale(sy, src[1], dst[1]) + 0.5);
}
 
static int scale_rev_x(int dx)
{
    return (int)floor(scale(dx + 0.5, dst[0], src[0]));
}
 
static int next_row(int sy, int dy)
{
    sy++;
 
    for (;;) {
        int y = scale_fwd_y(sy);
 
        if (y > dy)
            return sy - 1;
        sy++;
    }
}
 
static void alloc_buffers(void)
{
    if (nalloc >= ncols)
        return;
 
    nalloc = ncols;
    trans = G_realloc(trans, nalloc * sizeof(int));
}
 
/*!
   \brief Start drawing raster
 
   \param mask non-zero int for mask
   \param s source (map) extent (left, right, top, bottom)
   \param fd destination (image) extent (left, right, top, bottom)
 */
void PNG_begin_raster(int mask, int s[2][2], double fd[2][2])
{
    int d[2][2];
    int i;
 
    d[0][0] = (int)floor(fd[0][0] + 0.5);
    d[0][1] = (int)floor(fd[0][1] + 0.5);
    d[1][0] = (int)floor(fd[1][0] + 0.5);
    d[1][1] = (int)floor(fd[1][1] + 0.5);
 
    ncols = d[0][1] - d[0][0];
 
    memcpy(src, s, sizeof(src));
    memcpy(dst, d, sizeof(dst));
    masked = mask;
 
    alloc_buffers();
 
    for (i = 0; i < ncols; i++)
        trans[i] = scale_rev_x(d[0][0] + i);
}
 
/*!
   \brief Draw raster row
 
   \param n number of cells
   \param row raster row (starts at 0)
   \param red,grn,blu,nul red,green,blue and null value
 
   \return next row
 */
int PNG_raster(G_UNUSED int n, int row, const unsigned char *red,
               const unsigned char *grn, const unsigned char *blu,
               const unsigned char *nul)
{
    int d_y0 = scale_fwd_y(row + 0);
    int d_y1 = scale_fwd_y(row + 1);
    int d_rows = d_y1 - d_y0;
    int x0 = max(png.clip_left - dst[0][0], 0);
    int x1 = min(png.clip_rite - dst[0][0], ncols);
    int y0 = max(png.clip_top - d_y0, 0);
    int y1 = min(png.clip_bot - d_y0, d_rows);
    int x, y;
 
    if (y1 <= y0)
        return next_row(row, d_y1);
 
    for (x = x0; x < x1; x++) {
        int xx = dst[0][0] + x;
        int j = trans[x];
        int c;
 
        if (masked && nul && nul[j])
            continue;
 
        c = png_get_color(red[j], grn[j], blu[j], 0);
 
        for (y = y0; y < y1; y++) {
            int yy = d_y0 + y;
 
            png.grid[yy * png.width + xx] = c;
        }
    }
 
    png.modified = 1;
 
    return next_row(row, d_y1);
}