Crop images in image space (between 0 - 1)

virtual-programs/display/image.folk

@@ -3,7 +3,7 @@ On process "display" {
     set rotate $::rotate
     # TODO: Do this with a wish, instead of hard-coding the global dict.
     dict set ::pipelines "image" [Gpu::pipeline {sampler2D image vec2 imageSize
-                              vec2 pos float radians vec2 scale
+                              vec2 pos float radians vec2 scale vec4 crop
                               fn rotate} {
         vec2 a = pos + rotate(scale*-imageSize/2, -radians);
         vec2 b = pos + rotate(scale*vec2(imageSize.x, -imageSize.y)/2, -radians);
@@ -19,7 +19,10 @@ On process "display" {
         vec2 p = gl_FragCoord.xy;
         vec2 uv = invBilinear(p, a, b, c, d);
         if( max( abs(uv.x-0.5), abs(uv.y-0.5))<0.5 ) {
-            return texture(image, uv);
+            if ((crop[0] < uv.x) && (uv.x < crop[2]) &&
+                 (crop[1] < uv.y) && (uv.y < crop[3])) {
+                return texture(image, uv);
+            }
         }
         return vec4(0.0, 0.0, 0.0, 0.0);
     }]
@@ -108,6 +111,7 @@ On process "display" {
         set im [dict get $options image]
         set radians [dict get $options radians]
         set scale [dict_getdef $options scale 1.0]
+        set crop [dict_getdef $options crop [list 0. 0. 1.0 1.0]]
         if {[llength $scale] == 1} {
           set scale [list $scale $scale] 
         }
@@ -116,6 +120,6 @@ On process "display" {
 
         Wish the GPU draws pipeline "image" with arguments \
             [list $gim [list [image_t width $im] [image_t height $im]] \
-                 $center $radians $scale]
+                 $center $radians $scale $crop]
     }
 }