Implement cammy_image_split()

Implement cammy_image_split() to split an image's red, green and blue
channels into three separate channels

src/image.c

@@ -680,9 +680,84 @@ void cammy_image_copy(cammy_image *dest,
     }
 }
 
+static void bitmap_copy_channel(cammy_image *dest,
+                                cammy_image *src,
+                                cammy_image_point *to,
+                                cammy_image_region *from,
+                                int channel) {
+    size_t x, y;
+
+    int channels_dest = depth_channels(dest->depth),
+        channels_src  = depth_channels(src->depth);
+
+    for (y=from->y; y<from->y + from->height; y++) {
+        if (y >= dest->height) {
+            break;
+        }
+
+        for (x=0; x<from->x + from->width; x++) {
+            uint8_t v;
+
+            if (x >= dest->width) {
+                break;
+            }
+
+            v = bitmap_read_channel(src->buf, x, y, src->width, channels_src, channel);
+
+            bitmap_write(dest->buf, x, y, from->width, channels_dest, 0, 0, 0);
+            bitmap_write_channel(dest->buf, x, y, from->width, channels_dest, channel, v);
+        }
+    }
+}
+
 int cammy_image_split(cammy_image *image,
                       cammy_image **r,
                       cammy_image **g,
                       cammy_image **b) {
+    struct {
+        cammy_image **output;
+        int channel;
+    } outputs[3] = {
+        { r, 0 },
+        { g, 1 },
+        { b, 2 }
+    };
+
+    int i;
+
+    if (image->format != CAMMY_IMAGE_BITMAP) {
+        goto error_invalid_format;
+    }
+
+    for (i=0; i<3; i++) {
+        cammy_image **output = outputs[i].output;
+
+        cammy_image_point to = {
+            0, 0
+        };
+
+        cammy_image_region from = {
+            0, 0, image->width, image->height
+        };
+
+        if ((*output = cammy_image_new(image->format,
+                                       image->depth,
+                                       image->palette,
+                                       image->width,
+                                       image->height)) == NULL) {
+            goto error_image_new;
+        }
+
+        bitmap_copy_channel(*output, image, &to, &from, i);
+    }
+
     return 0;
+
+error_image_new:
+    while (--i >= 0) {
+        cammy_image_destroy(*(outputs[i].output));
+    }
+
+error_invalid_format:
+    return -1;
 }