Load any type of image

src/main.rs

@@ -1,12 +1,12 @@
+//! Image format is a buffer of `SCREEN_W * SCREEN_H + 1` bytes.
+//! The 4 least-significant bits of each byte is one pixel. The 4 most-significant bits are unused.
+//! Images are stored in landscape format, i.e. the first byte is the top-left pixel, and the
+//! second-to-last byte is the bottom-right pixel. The final byte is a null-terminator, and must be 0.
 use clap::Parser;
-use eyre::{Context, ensure, eyre};
+use eyre::{Context, bail, eyre};
+use image::ImageReader;
 use nix::ioctl_write_ptr;
-use std::{
-    fs::File,
-    io::Read,
-    os::fd::AsRawFd,
-    path::{Path, PathBuf},
-};
+use std::{fs::File, os::fd::AsRawFd, path::PathBuf};
 
 #[derive(Parser)]
 struct Opt {
@@ -14,11 +14,10 @@ struct Opt {
     pub path: PathBuf,
 }
 
-const SCREEN_W: usize = 1404;
-const SCREEN_H: usize = 1872;
+const SCREEN_W: usize = 1872;
+const SCREEN_H: usize = 1404;
 
-const BITS_PER_PIXEL: usize = 4;
-const FILE_SIZE: usize = SCREEN_W * SCREEN_H * BITS_PER_PIXEL / 8;
+const FILE_SIZE: usize = SCREEN_W * SCREEN_H + 1;
 
 // const SPI_IOC_MAGIC: u8 = b'k'; // Defined in linux/spi/spidev.h
 // const SPI_IOC_TYPE_MESSAGE: u8 = 0;
@@ -46,12 +45,29 @@ fn main() -> eyre::Result<()> {
     let opt = Opt::parse();
     color_eyre::install()?;
 
-    let image =
-        read_file(&opt.path).wrap_err_with(|| eyre!("Failed to read file at {:?}", opt.path))?;
+    let mut image = ImageReader::open(&opt.path)?.decode()?;
+
+    let image_dimensions = (image.width() as usize, image.height() as usize);
+
+    match image_dimensions {
+        (SCREEN_W, SCREEN_H) => {}
+        (SCREEN_H, SCREEN_W) => image = image.rotate270(),
+        _ => bail!("Image must be {SCREEN_W}x{SCREEN_H}"),
+    }
+
+    let image = image.to_luma8();
+    let mut pixels = image.into_vec();
+    for pixel in &mut pixels {
+        *pixel >>= 4; // convert 8-bit colorspace to 4-bits.
+    }
+    pixels.push(0u8); // add a null-terminator
+
+    // sanity check buffer length
+    assert!(pixels.len() == FILE_SIZE);
 
     let set_off_screen_data = DrmRockchipEbcOffScreen {
         info1: 0, // TODO: what is this?
-        ptr_screen_content: image.as_ptr(),
+        ptr_screen_content: pixels.as_ptr(),
     };
 
     let driver_file = File::options()
@@ -64,16 +80,3 @@ fn main() -> eyre::Result<()> {
 
     Ok(())
 }
-
-fn read_file(path: &Path) -> eyre::Result<Vec<u8>> {
-    let mut file = File::open(path)?;
-    let mut buf = vec![0u8; FILE_SIZE];
-    file.read_exact(&mut buf[..])
-        .wrap_err_with(|| eyre!("Expected a raw image file, of exactly {FILE_SIZE} bytes"))?;
-
-    // Try to read a single byte. If n != 0, it means the file was larger than FILE_SIZE
-    let n = file.read(&mut [0u8])?;
-    ensure!(n == 0, "File must be exacly {FILE_SIZE} bytes long");
-
-    Ok(buf)
-}