Write release note for PR 10392 (CPU Drawing) (#1854)

Co-authored-by: Alice Cecile <[email protected]>

release-content/0.15/release-notes/10392_CPU_Drawing.md

@@ -0,0 +1,61 @@
+There are many situations where you might want to just set the color of pixels
+from CPU code.  Procedural assets, certain art styles, or simply because
+it is easier. No need to bother with shaders and materials, when you just want
+to change a few specific pixels!
+
+In previous versions of Bevy, this was difficult and tedious. Bevy gives you
+access to the raw data bytes of an [`Image`], but you had to compute the byte
+offset corresponding to your desired pixel coordinate, make sure to encode your
+bytes with respect to the [`TextureFormat`], etc. Very low level!
+
+In Bevy 0.15, there are now user-friendly APIs for reading and writing the
+colors of pixels in an [`Image`]. The tricky low-level details are dealt with
+for you! You can even use `bevy_color`'s fancy color space APIs!
+
+```rust
+fn my_system(mut images: ResMut<Assets<Image>>, mut commands: Commands) {
+    // Create a new image.
+    let mut image = Image::new_fill(
+        // 64x64 size
+        Extent3d {
+            width: 64,
+            height: 64,
+            depth_or_array_layers: 1,
+        },
+        TextureDimension::D2,
+        &Srgba::WHITE.to_u8_array(),
+        TextureFormat::Rgba8UnormSrgb,
+        RenderAssetUsages::all(),
+    );
+
+    // This is new:
+
+    // Make the pixel at x: 23, y: 32 magenta
+    image.set_color_at(23, 32, Color::srgb(1.0, 0.0, 1.0))
+        .expect("Error writing color");
+
+    // Set the pixel at 10,10 to a color specified using the Oklch color space:
+    image.set_color_at(10, 10, Color::oklch(0.3, 0.2, 0.5))
+        .expect("Error writing color");
+
+    // read the bytes of the pixel we just wrote:
+    let bytes = image.pixel_bytes(UVec3::new(10, 10, 0)).unwrap();
+
+    // read the (approximate) color back (as sRGB):
+    let color = image.get_color_at(10, 10);
+
+    // We could add our new image to Bevy's assets
+    // and spawn a sprite to display it:
+    commands.spawn(Sprite {
+        image: images.add(image),
+        ..default()
+    });
+}
+```
+
+Note: The [`Color`]-based methods are lossy. They have to convert to/from the
+[`Image`]'s [`TextureFormat`]. If you read back the color you wrote, it will be slightly different.
+
+[`Image`]: https://docs.rs/bevy/0.15.0-rc.3/bevy/prelude/struct.Image.html
+[`TextureFormat`]: https://docs.rs/bevy/0.15.0-rc.3/bevy/render/render_resource/enum.TextureFormat.html
+[`Color`]: https://docs.rs/bevy/0.15.0-rc.3/bevy/color/enum.Color.html

release-content/0.15/release-notes/_release-notes.toml

@@ -40,6 +40,13 @@ contributors = ["@kristoff3r", "@tychedelia", "@JMS55"]
 prs = [14876]
 file_name = "14876_Add_Order_Independent_Transparency.md"
 
+[[release_notes]]
+title = "User-Friendly CPU Drawing"
+authors = ["@inodentry"]
+contributors = []
+prs = [10392]
+file_name = "10392_CPU_Drawing.md"
+
 [[release_notes]]
 title = "Entity Picking / Selection"
 authors = ["@aevyrie", "@NthTensor", "@TotalKrill", "@jnhyatt", "@Jondolf"]