refactor: split kra (krita) logic into image hook

may further split this into its own crate;
seems quite useful! (albeit somewhat short and easy)

since there aren't any runtime dependancies,
it could even go into image-extras maybe

src/kra.rs

@@ -0,0 +1,41 @@
+use std::{
+    ffi::OsString,
+    io::{self, Read},
+};
+
+use image::{
+    ImageDecoder, ImageError, ImageReader, ImageResult,
+    error::DecodingError,
+    hooks::{self, GenericReader},
+};
+use zip::ZipArchive;
+
+pub fn register() -> bool {
+    hooks::register_decoding_hook(OsString::from("kra"), Box::new(hook))
+}
+
+fn hook<'a>(reader: GenericReader<'a>) -> ImageResult<Box<dyn ImageDecoder + 'a>> {
+    let mut zip = ZipArchive::new(reader).map_err(|e| {
+        ImageError::Decoding(DecodingError::new(
+            image::error::ImageFormatHint::PathExtension("kra".into()),
+            e,
+        ))
+    })?;
+
+    let mut reader = zip.by_name("mergedimage.png").map_err(|e| {
+        ImageError::Decoding(DecodingError::new(
+            image::error::ImageFormatHint::PathExtension("kra".into()),
+            e,
+        ))
+    })?;
+
+    // reading it all and wrapping it with a Cursor
+    // is the only way I know to give it Seek
+    // (which is required by ImageReader)
+    let mut buf = Vec::new();
+    reader.read_to_end(&mut buf)?;
+
+    let image_reader = ImageReader::with_format(io::Cursor::new(buf), image::ImageFormat::Png);
+
+    Ok(Box::new(image_reader.into_decoder()?))
+}

src/main.rs

@@ -7,6 +7,7 @@ use iced::{
 };
 use image::{EncodableLayout, RgbaImage, imageops};
 
+mod kra;
 mod utils;
 
 #[derive(Clone, Debug)]
@@ -209,6 +210,7 @@ impl State {
 
 fn main() -> Result<(), iced::Error> {
     jxl_oxide::integration::register_image_decoding_hook();
+    kra::register();
 
     iced::application(State::new, State::update, State::view)
         .subscription(State::subscription)

src/utils.rs

@@ -1,80 +1,12 @@
-use std::{
-    fs,
-    io::{self, Read},
-    path::{Path, PathBuf},
-};
+use std::path::{Path, PathBuf};
 
 use iced::widget;
 use image::{DynamicImage, ImageDecoder, ImageReader, RgbaImage};
 use rfd::FileDialog;
-use zip::ZipArchive;
 
 pub fn load_image(path: impl AsRef<Path>) -> Result<RgbaImage, String> {
     let path = path.as_ref();
 
-    let decoded_image = if path.extension().is_some_and(|ext| ext == "kra") {
-        let reader = match fs::File::open(path).map(io::BufReader::new) {
-            Ok(r) => r,
-            Err(e) => {
-                return Err(format!(
-                    "failed to create reader for '{}': {e}",
-                    path.display()
-                ));
-            }
-        };
-
-        let mut zip = match ZipArchive::new(reader) {
-            Ok(z) => z,
-            Err(e) => {
-                return Err(format!(
-                    "failed to open zip archive '{}': {e}",
-                    path.display()
-                ));
-            }
-        };
-
-        let mut reader = match zip.by_name("mergedimage.png") {
-            Ok(r) => r,
-            Err(e) => {
-                return Err(format!(
-                    "failed to open file in zip archive '{}': {e}",
-                    path.display()
-                ));
-            }
-        };
-
-        // reading it all and wrapping it with a Cursor
-        // is the only way I know to give it Seek
-        // (which is required by ImageReader)
-        let mut buf = Vec::new();
-        if let Err(e) = reader.read_to_end(&mut buf) {
-            return Err(format!(
-                "error when reading file in zip archive '{}': {e}",
-                path.display()
-            ));
-        };
-
-        let image_reader = ImageReader::with_format(io::Cursor::new(buf), image::ImageFormat::Png);
-
-        let decoder = match image_reader.into_decoder() {
-            Ok(d) => d,
-            Err(e) => {
-                return Err(format!(
-                    "failed to create decoder for '{}': {e}",
-                    path.display()
-                ));
-            }
-        };
-
-        let decoded_image = match DynamicImage::from_decoder(decoder) {
-            Ok(i) => i,
-            Err(e) => {
-                return Err(format!("failed to decode image '{}': {e}", path.display()));
-            }
-        };
-
-        decoded_image
-    } else {
     let image_reader = match ImageReader::open(path) {
         Ok(r) => r,
         Err(e) => {
@@ -95,8 +27,6 @@ pub fn load_image(path: impl AsRef<Path>) -> Result<RgbaImage, String> {
         }
     };
 
-        // we don't need to check this for the kra branch
-        // since PNGs don't have metadata oreintation
     let oreintation = match decoder.orientation() {
         Ok(o) => o,
         Err(e) => {
@@ -116,9 +46,6 @@ pub fn load_image(path: impl AsRef<Path>) -> Result<RgbaImage, String> {
 
     decoded_image.apply_orientation(oreintation);
 
-        decoded_image
-    };
-
     Ok(decoded_image.into_rgba8())
 }
 pub fn pick_image() -> Result<PathBuf, String> {