Blargh

src/main.rs

@@ -70,7 +70,7 @@ fn load_wallpaper(path: &Path) -> eyre::Result<GrayAlphaImage> {
 
     match image_dimensions {
         (SCREEN_W, SCREEN_H) => {}
-        (SCREEN_H, SCREEN_W) => image = image.rotate270(),
+        (SCREEN_H, SCREEN_W) => image = image.rotate90(),
         _ => bail!("Image must be {SCREEN_W}x{SCREEN_H}"),
     }
 
@@ -114,12 +114,20 @@ fn image_to_offimage_buffer(image: GrayAlphaImage) -> eyre::Result<Box<[u8; IOCT
     let image = image.into_vec();
 
     ensure!(
-        image.len() / 2 + 1 == IOCTL_BUFFER_SIZE,
+        image.len() / 2 == SCREEN_W * SCREEN_H,
         "Invalid size of image backing buffer. Bug?",
     );
 
+    // iterate over pixel coordinates
+    let xs = 0..SCREEN_W;
+    let ys = 0..SCREEN_H;
+    let ys = ys.rev(); // flip `y`, it's reversed in the ioctl buffer.
+    let coords = ys.flat_map(|y| xs.clone().map(move |x| (x, y)));
+    // coordinates to indices
+    let indices = coords.map(|(x, y)| y * SCREEN_W + x);
+
     // Iterate over pixels and copy them into `buf`.
-    for (i, pixel) in (0..buf.len() - 1).rev().zip(image.chunks_exact(2)) {
+    for (i, pixel) in indices.zip(image.chunks_exact(2)) {
         let &[gray, alpha] = pixel else {
             unreachable!()
         };