pngdriver/Raster.c

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#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));
}

void PNG_begin_scaled_raster(int mask, int s[2][2], int d[2][2])
{
    int i;

    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);
}

int PNG_scaled_raster(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(clip_left - dst[0][0], 0);
    int x1 = min(clip_rite - dst[0][0], ncols);
    int y0 = max(clip_top - d_y0, 0);
    int y1 = min(clip_bot - d_y0, d_rows);
    int x, y;

    if (y1 <= y0)
        return next_row(row, d_y0);

    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 = get_color(red[j], grn[j], blu[j], 0);

        for (y = y0; y < y1; y++) {
            int yy = d_y0 + y;

            grid[yy * width + xx] = c;
        }
    }

    modified = 1;

    return next_row(row, d_y1);
}