Add a screenshot utility

examples/screenshot.rs

@@ -0,0 +1,49 @@
+use image::{DynamicImage, ImageOutputFormat};
+use libremarkable::device::CURRENT_DEVICE;
+use libremarkable::framebuffer::common::*;
+use libremarkable::framebuffer::core::*;
+use libremarkable::framebuffer::*;
+use libremarkable::image::RgbImage;
+use std::fs::OpenOptions;
+
+fn main() {
+    let fb = Framebuffer::from_path(CURRENT_DEVICE.get_framebuffer_path());
+    let width = DISPLAYWIDTH as u32;
+    let height = DISPLAYHEIGHT as u32;
+    let contents = fb
+        .dump_region(mxcfb_rect {
+            top: 0,
+            left: 0,
+            width,
+            height,
+        })
+        .expect("dumping image buffer with known dimensions should succeed")
+        .chunks_exact(2)
+        .flat_map(|c| color::NATIVE_COMPONENTS(c[0], c[1]).to_rgb8())
+        .collect::<Vec<_>>();
+
+    let image =
+        RgbImage::from_raw(width, height, contents).expect("unable to construct the rgb image");
+
+    let args = std::env::args().collect::<Vec<_>>();
+
+    match args.get(1) {
+        Some(path) => {
+            let mut output_file = OpenOptions::new()
+                .write(true)
+                .create(true)
+                .truncate(false)
+                .open(path)
+                .expect("Invalid path provided as argument!");
+            DynamicImage::ImageRgb8(image)
+                .write_to(&mut output_file, ImageOutputFormat::Png)
+                .expect("failed while writing to output file");
+        }
+        None => {
+            let mut stdout = std::io::stdout();
+            DynamicImage::ImageRgb8(image)
+                .write_to(&mut stdout, ImageOutputFormat::Png)
+                .expect("failed while writing to stdout");
+        }
+    }
+}