feat: implement cbz writing and pdf reading

src/formats/cbz.rs

@@ -1,6 +1,6 @@
 use std::ffi::OsStr;
 use std::fs::File;
-use std::io::Read;
+use std::io::{Read, Write};
 use std::path::Path;
 
 use anyhow::Result;
@@ -9,7 +9,7 @@ use zip::ZipArchive;
 
 use crate::model::{Document, ImagePage};
 
-use super::FormatReader;
+use super::{FormatReader, FormatWriter};
 
 pub struct CbzReader;
 
@@ -51,3 +51,40 @@ impl FormatReader for CbzReader {
         Ok(Document::new(pages))
     }
 }
+
+pub struct CbzWriter;
+
+impl FormatWriter for CbzWriter {
+    fn write(&self, doc: &Document, output: &Path) -> Result<()> {
+        use zip::write::SimpleFileOptions;
+        let file = File::create(output)?;
+        let mut zip = zip::ZipWriter::new(file);
+        let options = SimpleFileOptions::default();
+
+        for (idx, page) in doc.pages.iter().enumerate() {
+            let mut name = page.name.clone();
+            if Path::new(&name).extension().and_then(OsStr::to_str) != Some("jpg") {
+                name = format!("{:03}.jpg", idx + 1);
+            }
+            zip.start_file(&name, options)?;
+            if let Some(dct) = &page.jpeg_dct {
+                zip.write_all(dct)?;
+            } else {
+                // Encode to JPEG
+                let rgb = page.image.to_rgb8();
+                let (w, h) = (rgb.width(), rgb.height());
+                let mut cursor = std::io::Cursor::new(Vec::new());
+                {
+                    let mut enc =
+                        image::codecs::jpeg::JpegEncoder::new_with_quality(&mut cursor, 85);
+                    enc.encode(&rgb.into_raw(), w, h, image::ColorType::Rgb8.into())?;
+                }
+                let data = cursor.into_inner();
+                zip.write_all(&data)?;
+            }
+        }
+
+        zip.finish()?;
+        Ok(())
+    }
+}