Make cairo driver rescale rasters rather than having cairo do it (ticket https://trac.osgeo.org/grass/ticket/2403)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@63582 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/cairodriver/raster.c

@@ -12,21 +12,58 @@
   \author Glynn Clements  
 */
 
+#include <math.h>
 
 #include "cairodriver.h"
 #include <grass/glocale.h>
 
 #define MAX_IMAGE_SIZE 32767
+#ifndef MIN
+#define MIN(a,b) ((a)<(b)?(a):(b))
+#endif
+#ifndef MAX
+#define MAX(a,b) ((a)>(b)?(a):(b))
+#endif
 
 static int src_t, src_b, src_l, src_r, src_w, src_h;
-static double dst_t, dst_b, dst_l, dst_r, dst_w, dst_h;
+static int dst_t, dst_b, dst_l, dst_r, dst_w, dst_h;
+
+static int *trans;
 
 static cairo_surface_t *src_surf;
 static unsigned char *src_data;
-static int src_stride;
+static int src_stride, ca_row;
 
 static int masked;
 
+static double scale(double k, int src_0, int src_1, int dst_0, int dst_1)
+{
+    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_t, src_b, dst_t, dst_b) + 0.5);
+}
+
+static int scale_rev_x(int dx)
+{
+    return (int)floor(scale(dx + 0.5, dst_l, dst_r, src_l, src_r));
+}
+
+static int next_row(int sy, int dy)
+{
+    sy++;
+
+    for (;;) {
+	int y = scale_fwd_y(sy);
+
+	if (y > dy)
+	    return sy - 1;
+	sy++;
+    }
+}
+
 /*!
   \brief Start drawing raster
 
@@ -38,6 +75,7 @@ static int masked;
 */
 void Cairo_begin_raster(int mask, int s[2][2], double d[2][2])
 {
+    int i;
     cairo_status_t status;
     
     masked = mask;
@@ -50,36 +88,42 @@ void Cairo_begin_raster(int mask, int s[2][2], double d[2][2])
     src_w = src_r - src_l;
     src_h = src_b - src_t;
 
-    dst_l = d[0][0];
-    dst_r = d[0][1];
-    dst_t = d[1][0];
-    dst_b = d[1][1];
+    dst_l = (int) floor(d[0][0] + 0.5);
+    dst_r = (int) floor(d[0][1] + 0.5);
+    dst_t = (int) floor(d[1][0] + 0.5);
+    dst_b = (int) floor(d[1][1] + 0.5);
 
     dst_w = dst_r - dst_l;
     dst_h = dst_b - dst_t;
 
     G_debug(1, "Cairo_begin_raster(): masked=%d, src_lrtb=%d %d %d %d -> w/h=%d/%d, "
-            "dst_lrtb=%f %f %f %f -> w/h=%f %f",
+            "dst_lrtb=%d %d %d %d -> w/h=%d %d",
             masked, src_l, src_r, src_t, src_b, src_w, src_h,
             dst_l, dst_r, dst_t, dst_b, dst_w, dst_h);
 
     /* create source surface */
-    src_surf = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, src_w, src_h);
+    src_surf = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, ca.width, ca.height);
     status = cairo_surface_status(src_surf);
     if (status != CAIRO_STATUS_SUCCESS)
         G_fatal_error("%s - %s - size: %dx%d (cairo limit: %dx%d)",
                       _("Failed to create cairo surface"),
-                      cairo_status_to_string (status), src_w, src_h,
+                      cairo_status_to_string (status), ca.width, ca.height,
                       MAX_IMAGE_SIZE, MAX_IMAGE_SIZE);
-    
+
     src_data = cairo_image_surface_get_data(src_surf);
     src_stride = cairo_image_surface_get_stride(src_surf);
+    ca_row = 0;
+
+    /* allocate buffer for down-sampling data */
+    trans = G_malloc(dst_w * sizeof(int));
+    for (i = 0; i < dst_w; i++)
+        trans[i] = scale_rev_x(dst_l + i);
 }
 
 /*!
   \brief Draw raster row
 
-  \param n number of cell
+  \param n number of cells
   \param row raster row (starting at 0)
   \param red,grn,blu,nul red,green,blue and null value
 
@@ -89,27 +133,45 @@ int Cairo_raster(int n, int row,
 		 const unsigned char *red, const unsigned char *grn,
 		 const unsigned char *blu, const unsigned char *nul)
 {
-    int i;
-    unsigned int *dst;
-
-    dst = (unsigned int *)(src_data + (row - src_t) * src_stride);
-
-    G_debug(3, "Cairo_raster(): n=%d row=%d", n, row);
-
-    for (i = 0; i < n; i++) {
-	if (masked && nul && nul[i])
-	    *dst++ = 0;
+    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(0        - dst_l, 0);
+    int x1 = MIN(ca.width - dst_l, dst_w);
+    int y0 = MAX(0         - d_y0, 0);
+    int y1 = MIN(ca.height - d_y0, d_rows);
+    int x, y;
+
+    if (y1 <= y0)
+        return next_row(row, d_y1);
+
+    G_debug(3, "Cairo_raster(): row=%d", row);
+
+    for (x = x0; x < x1; x++) {
+	int xx = dst_l + x;
+        int j = trans[x];
+	unsigned int c;
+
+	if (masked && nul && nul[j])
+	    c = 0;
 	else {
-	    unsigned int r = red[i];
-	    unsigned int g = grn[i];
-	    unsigned int b = blu[i];
+	    unsigned int r = red[j];
+	    unsigned int g = grn[j];
+	    unsigned int b = blu[j];
 	    unsigned int a = 0xFF;
-
-	    *dst++ = (a << 24) + (r << 16) + (g << 8) + (b << 0);
+	    c = (a << 24) + (r << 16) + (g << 8) + (b << 0);
 	}
+
+	for (y = y0; y < y1; y++) {
+	    int yy = d_y0 + y;
+	    *(unsigned int *)(src_data + yy * src_stride + xx * 4) = c;
+        }
     }
 
-    return row + 1;
+    ca.modified = 1;
+    ca_row++;
+
+    return next_row(row, d_y1);
 }
 
 /*!
@@ -121,8 +183,8 @@ void Cairo_end_raster(void)
 
     /* paint source surface onto destination (scaled) */
     cairo_save(cairo);
-    cairo_translate(cairo, dst_l, dst_t);
-    cairo_scale(cairo, dst_w / src_w, dst_h / src_h);
+    /* cairo_translate(cairo, dst_l, dst_t); */
+    /* cairo_scale(cairo, dst_w / src_w, dst_h / src_h); */
     cairo_surface_mark_dirty(src_surf);
     cairo_set_source_surface(cairo, src_surf, 0, 0);
     cairo_pattern_set_filter(cairo_get_source(cairo), CAIRO_FILTER_NEAREST);
@@ -130,6 +192,7 @@ void Cairo_end_raster(void)
     cairo_restore(cairo);
 
     /* cleanup */
+    G_free(trans);
     cairo_surface_destroy(src_surf);
     ca.modified = 1;
 }