Add example of loading and showing an image with eframe/egui

Closes https://github.com/emilk/egui/pull/700

Cargo.lock

@@ -784,6 +784,7 @@ dependencies = [
  "egui_glium",
  "egui_web",
  "epi",
+ "image",
 ]
 
 [[package]]

eframe/Cargo.toml

@@ -34,6 +34,9 @@ egui_glium = { version = "0.14.0", path = "../egui_glium", default-features = fa
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 egui_web = { version = "0.14.0", path = "../egui_web", default-features = false }
 
+[dev-dependencies]
+image = { version = "0.23", default-features = false, features = ["png"] }
+
 [features]
 default = ["default_fonts"]
 

eframe/examples/image.rs

@@ -0,0 +1,47 @@
+use eframe::{egui, epi};
+
+#[derive(Default)]
+struct MyApp {
+    texture: Option<egui::TextureId>,
+}
+
+impl epi::App for MyApp {
+    fn name(&self) -> &str {
+        "Show an image with eframe/egui"
+    }
+
+    fn update(&mut self, ctx: &egui::CtxRef, frame: &mut epi::Frame<'_>) {
+        if self.texture.is_none() {
+            // Load the image:
+            let image_data = include_bytes!("rust-logo-512x512.png");
+            use image::GenericImageView;
+            let image = image::load_from_memory(image_data).expect("Failed to load image");
+            let image_buffer = image.to_rgba8();
+            let size = (image.width() as usize, image.height() as usize);
+            let pixels = image_buffer.into_vec();
+            assert_eq!(size.0 * size.1 * 4, pixels.len());
+            let pixels: Vec<_> = pixels
+                .chunks_exact(4)
+                .map(|p| egui::Color32::from_rgba_unmultiplied(p[0], p[1], p[2], p[3]))
+                .collect();
+
+            // Allocate a texture:
+            let texture = frame
+                .tex_allocator()
+                .alloc_srgba_premultiplied(size, &pixels);
+            self.texture = Some(texture);
+        }
+
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.heading("Here is an image for you:");
+            if let Some(texture) = self.texture {
+                ui.image(texture, egui::Vec2::splat(256.0));
+            }
+        });
+    }
+}
+
+fn main() {
+    let options = eframe::NativeOptions::default();
+    eframe::run_native(Box::new(MyApp::default()), options);
+}

eframe/examples/rust-logo-license.txt

@@ -0,0 +1 @@
+Rust logo by Mozilla, from https://github.com/rust-lang/rust-artwork