--- a/render_mandelbrot.c	Tue Jun 17 18:15:43 2008 +0300
+++ b/render_mandelbrot.c	Tue Jun 17 19:08:05 2008 +0300
@@ -18,9 +18,9 @@
     h_scale = ctx->img_h/absdelta(ctx->y1, ctx->y2);
     
     // start rendering!
-    for (img_y=0; img_y < ctx->img_h; img_y++) {
+    for (img_y=ctx->img_top; img_y < ctx->img_bottom; img_y += ctx->img_y_step) {
         // render the current row
-        for (img_x=0; img_x < ctx->img_w; img_x++) {
+        for (img_x=ctx->img_left; img_x < ctx->img_right; img_x += ctx->img_x_step) {
             x = 0;
             y = 0;
             x0 = img_x/w_scale + ctx->x1;
@@ -37,7 +37,7 @@
                 iter--;
             }
             
-            (*ctx->local_rowbuf_addr)[img_x] = iter;
+            (*ctx->local_rowbuf_addr)[img_x - ctx->img_left] = iter;
         }
 
         // row cb