--- a/render.c	Tue Jun 17 18:15:43 2008 +0300
+++ b/render.c	Tue Jun 17 19:08:05 2008 +0300
@@ -39,6 +39,12 @@
     ctx->img_w = img_w;
     ctx->img_h = img_h;
 
+    // default render region...
+    ctx->img_left = ctx->img_top = 0;
+    ctx->img_right = img_w;
+    ctx->img_bottom = img_h;
+    ctx->img_x_step = ctx->img_y_step = 1;
+
     return 0;
 }