New function to make sure that the weights sum up to the correct total

	* pixops/pixops.c (correct_total): New function to make sure
	that the weights sum up to the correct total without introducing
	negative weights.
	(tile_make_weights, bilinear_make_fast_weights,
	bilinear_make_weights): Use correct_total.

diff --git a/gdk-pixbuf/ChangeLog b/gdk-pixbuf/ChangeLog
index 9905a93be9c2303d17031c8d5cad16519b271dac..4d6448f347f92d16da02857293652b83a23cbb3e 100644 (file)
--- a/gdk-pixbuf/ChangeLog
+++ b/gdk-pixbuf/ChangeLog
@@ -1,3 +1,11 @@
+2002-02-15  Matthias Clasen  <matthias@YAST_ASK>
+
+       * pixops/pixops.c (correct_total): New function to make sure
+       that the weights sum up to the correct total without introducing
+       negative weights.
+       (tile_make_weights, bilinear_make_fast_weights, 
+       bilinear_make_weights): Use correct_total.
+
 2002-02-10  Matthias Clasen  <matthias@local>
 
        * test-images.h (tiff1_test_3), test-loaders.c (main): Add a

diff --git a/gdk-pixbuf/pixops/pixops.c b/gdk-pixbuf/pixops/pixops.c
index 0bcbcec011150b72df03a316c5a1fb6982ccd042..a84de8525731368846e3c37cf2a9506161a79462 100644 (file)
--- a/gdk-pixbuf/pixops/pixops.c
+++ b/gdk-pixbuf/pixops/pixops.c
@@ -1077,6 +1077,25 @@ pixops_process (guchar         *dest_buf,
   g_free (line_bufs);
 }
 
+static void 
+correct_total (int    *weights, 
+              int    n_x, 
+              int    n_y,
+              int    total, 
+              double overall_alpha)
+{
+  int correction = (int)(0.5 + 65536 * overall_alpha) - total;
+  int i;
+  for (i = n_x * n_y - 1; i >= 0; i--) 
+    {
+      if (*(weights + i) + correction >= 0) 
+       {
+         *(weights + i) += correction;
+         break;
+       }
+    }
+}  
+
 static void
 tile_make_weights (PixopsFilter *filter, double x_scale, double y_scale, double overall_alpha)
 {
@@ -1143,8 +1162,8 @@ tile_make_weights (PixopsFilter *filter, double x_scale, double y_scale, double
                total += weight;
                *(pixel_weights + n_x * i + j) = weight;
              }
-
-           *(pixel_weights + n_x * n_y - 1) += (int)(0.5 + 65536 * overall_alpha) - total;
+           
+           correct_total (pixel_weights, n_x, n_y, total, overall_alpha);
          }
       }
 }
@@ -1193,7 +1212,7 @@ bilinear_make_fast_weights (PixopsFilter *filter, double x_scale, double y_scale
        double y = (double)i_offset / SUBSAMPLE;
        int i,j;
        int total = 0;
-       
+
        if (x_scale > 1.0)      /* Bilinear */
          {
            for (i = 0; i < n_x; i++)
@@ -1266,7 +1285,7 @@ bilinear_make_fast_weights (PixopsFilter *filter, double x_scale, double y_scale
              total += weight;
            }
 
-       *(pixel_weights + n_x * n_y - 1) += (int)(0.5 + 65536 * overall_alpha) - total;
+       correct_total (pixel_weights, n_x, n_y, total, overall_alpha);
       }
 
   g_free (x_weights);
@@ -1352,13 +1371,13 @@ bilinear_make_weights (PixopsFilter *filter, double x_scale, double y_scale, dou
        double y = (double)i_offset / SUBSAMPLE;
        int i,j;
        int total = 0;
-       
+
        for (i = 0; i < n_y; i++)
          for (j = 0; j < n_x; j++)
            {
              double w;
              int weight;
-
+             
              w = bilinear_quadrant  (0.5 + j - (x + 1 / x_scale), 0.5 + j - x, 0.5 + i - (y + 1 / y_scale), 0.5 + i - y);
              w += bilinear_quadrant (1.5 + x - j, 1.5 + (x + 1 / x_scale) - j, 0.5 + i - (y + 1 / y_scale), 0.5 + i - y);
              w += bilinear_quadrant (0.5 + j - (x + 1 / x_scale), 0.5 + j - x, 1.5 + y - i, 1.5 + (y + 1 / y_scale) - i);
@@ -1367,8 +1386,8 @@ bilinear_make_weights (PixopsFilter *filter, double x_scale, double y_scale, dou
              *(pixel_weights + n_x * i + j) = weight;
              total += weight;
            }
-
-       *(pixel_weights + n_x * n_y - 1) += (int)(0.5 + 65536 * overall_alpha) - total;
+       
+       correct_total (pixel_weights, n_x, n_y, total, overall_alpha);
       }
 }
 
@@ -1444,7 +1463,7 @@ pixops_composite_color (guchar         *dest_buf,
       dest_channels == 4 && src_channels == 4 && src_has_alpha && !dest_has_alpha && found_mmx)
     line_func = composite_line_color_22_4a4_mmx_stub;
   else
-#endif    
+#endif
     line_func = composite_line_color;
   
   pixops_process (dest_buf, render_x0, render_y0, render_x1, render_y1,