libart 2.3.16

[swftools.git] / lib / art / art_rgb_affine_private.c

diff --git a/lib/art/art_rgb_affine_private.c b/lib/art/art_rgb_affine_private.c
new file mode 100644 (file)
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+++ b/lib/art/art_rgb_affine_private.c
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+/* Libart_LGPL - library of basic graphic primitives
+ * Copyright (C) 1998 Raph Levien
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+#include "art_rgb_affine_private.h"
+
+#include <math.h>
+#include "art_misc.h"
+#include "art_point.h"
+#include "art_affine.h"
+
+/* Private functions for the rgb affine image compositors - primarily,
+   the determination of runs, eliminating the need for source image
+   bbox calculation in the inner loop. */
+
+/* Determine a "run", such that the inverse affine of all pixels from
+   (x0, y) inclusive to (x1, y) exclusive fit within the bounds
+   of the source image.
+
+   Initial values of x0, x1, and result values stored in first two
+   pointer arguments.
+*/
+
+#define EPSILON 1e-6
+
+void
+art_rgb_affine_run (int *p_x0, int *p_x1, int y,
+                   int src_width, int src_height,
+                   const double affine[6])
+{
+  int x0, x1;
+  double z;
+  double x_intercept;
+  int xi;
+
+  x0 = *p_x0;
+  x1 = *p_x1;
+
+  /* do left and right edges */
+  if (affine[0] > EPSILON)
+    {
+      z = affine[2] * (y + 0.5) + affine[4];
+      x_intercept = -z / affine[0];
+      xi = ceil (x_intercept + EPSILON - 0.5);
+      if (xi > x0)
+       x0 = xi;
+      x_intercept = (-z + src_width) / affine[0];
+      xi = ceil (x_intercept - EPSILON - 0.5);
+      if (xi < x1)
+       x1 = xi;
+    }
+  else if (affine[0] < -EPSILON)
+    {
+      z = affine[2] * (y + 0.5) + affine[4];
+      x_intercept = (-z + src_width) / affine[0];
+      xi = ceil (x_intercept + EPSILON - 0.5);
+      if (xi > x0)
+       x0 = xi;
+      x_intercept = -z / affine[0];
+      xi = ceil (x_intercept - EPSILON - 0.5);
+      if (xi < x1)
+       x1 = xi;
+    }
+  else
+    {
+      z = affine[2] * (y + 0.5) + affine[4];
+      if (z < 0 || z >= src_width)
+       {
+         *p_x1 = *p_x0;
+         return;
+       }
+    }
+
+  /* do top and bottom edges */
+  if (affine[1] > EPSILON)
+    {
+      z = affine[3] * (y + 0.5) + affine[5];
+      x_intercept = -z / affine[1];
+      xi = ceil (x_intercept + EPSILON - 0.5);
+      if (xi > x0)
+       x0 = xi;
+      x_intercept = (-z + src_height) / affine[1];
+      xi = ceil (x_intercept - EPSILON - 0.5);
+      if (xi < x1)
+       x1 = xi;
+    }
+  else if (affine[1] < -EPSILON)
+    {
+      z = affine[3] * (y + 0.5) + affine[5];
+      x_intercept = (-z + src_height) / affine[1];
+      xi = ceil (x_intercept + EPSILON - 0.5);
+      if (xi > x0)
+       x0 = xi;
+      x_intercept = -z / affine[1];
+      xi = ceil (x_intercept - EPSILON - 0.5);
+      if (xi < x1)
+       x1 = xi;
+    }
+  else
+    {
+      z = affine[3] * (y + 0.5) + affine[5];
+      if (z < 0 || z >= src_height)
+       {
+         *p_x1 = *p_x0;
+         return;
+       }
+    }
+
+  *p_x0 = x0;
+  *p_x1 = x1;
+}