Can read image from memory

src/lib.rs

@@ -6,6 +6,7 @@
 use std::path::Path;
 
 use anyhow::anyhow;
+use image::DynamicImage;
 
 /// Embed the image from `image_filename` into `music_filename`, in-place. Any errors reading ID3
 /// tags from the music file or parsing the image get propagated upwards.
@@ -14,10 +15,21 @@ use anyhow::anyhow;
 /// Tags get written as ID3v2.3.
 ///
 pub fn embed_image(music_filename: &Path, image_filename: &Path) -> anyhow::Result<()> {
-    let mut tag = read_tag(music_filename)?;
     let image = image::open(&image_filename).
         map_err(|e| anyhow!("Error reading image {:?}: {}", image_filename, e))?;
 
+    embed_image_from_memory(music_filename, &image)
+}
+
+/// Embed the image `image` into `music_filename`, in-place. Any errors reading ID3
+/// tags from the music file get propagated upwards.
+///
+/// The image is encoded as a JPEG with a 90% quality setting, and embedded as a "Front cover".
+/// Tags get written as ID3v2.3.
+///
+pub fn embed_image_from_memory(music_filename: &Path, image: &image::DynamicImage) -> anyhow::Result<()> {
+    let mut tag = read_tag(music_filename)?;
+
     let mut encoded_image_bytes = Vec::new();
     // Unwrap: Writing to a Vec should always succeed;
     image.write_to(&mut encoded_image_bytes, image::ImageOutputFormat::Jpeg(90)).unwrap();
@@ -42,19 +54,23 @@ pub fn embed_image(music_filename: &Path, image_filename: &Path) -> anyhow::Resu
 /// there's no embedded images in the mp3 file.
 ///
 pub fn extract_first_image(music_filename: &Path, image_filename: &Path) -> anyhow::Result<()> {
+    extract_first_image_as_img(music_filename)?
+        .save(&image_filename).
+        map_err(|e| anyhow!("Couldn't write image file {:?}: {}", image_filename, e))
+}
+
+/// Extract the first found embedded image from `music_filename` and return it as image object
+///
+/// Any errors from parsing id3 tags will be propagated. The function will also return an error if
+/// there's no embedded images in the mp3 file.
+///
+pub fn extract_first_image_as_img(music_filename: &Path) -> anyhow::Result<DynamicImage> {
     let tag = read_tag(music_filename)?;
     let first_picture = tag.pictures().next();
 
     if let Some(p) = first_picture {
-        match image::load_from_memory(&p.data) {
+        return image::load_from_memory(&p.data)
-            Ok(image) => {
+            .map_err(|e| anyhow!("Couldn't load image: {}", e));
-                image.save(&image_filename).
-                    map_err(|e| anyhow!("Couldn't write image file {:?}: {}", image_filename, e))?;
-            },
-            Err(e) => return Err(anyhow!("Couldn't load image: {}", e)),
-        };
-
-        Ok(())
     } else {
         Err(anyhow!("No image found in music file"))
     }

tests/test_processing.rs

@@ -1,9 +1,10 @@
 use std::env;
 use std::fs;
-use std::path::{PathBuf, Path};
 use std::ops::Deref;
+use std::path::{Path, PathBuf};
 
 use tempfile::TempDir;
+
 use id3_image::*;
 
 struct Fixture {
@@ -45,6 +46,7 @@ fn read_tag(path: &Path) -> id3::Tag {
     id3::Tag::read_from_path(path).unwrap()
 }
 
+
 #[test]
 fn test_unsuccessful_image_embedding() {
     let song = Fixture::copy("attempt_1_no_image.mp3");
@@ -67,7 +69,7 @@ fn test_successful_jpeg_image_embedding() {
     let image = Fixture::copy("attempt_1.jpg");
 
     let tag = read_tag(&song);
-    assert!(tag.pictures().count() == 0);
+    assert_eq!(tag.pictures().count(), 0);
 
     embed_image(&song, &image).unwrap();
 
@@ -92,7 +94,7 @@ fn test_successful_png_image_embedding() {
     let image = Fixture::copy("attempt_1.png");
 
     let tag = read_tag(&song);
-    assert!(tag.pictures().count() == 0);
+    assert_eq!(tag.pictures().count(), 0);
 
     embed_image(&song, &image).unwrap();
 
@@ -100,6 +102,38 @@ fn test_successful_png_image_embedding() {
     assert!(tag.pictures().count() > 0);
 }
 
+#[test]
+fn test_successful_png_image_embedding_from_memory() {
+    let song = Fixture::copy("attempt_1_no_image.mp3");
+    let image = Fixture::copy("attempt_1.png");
+
+    let tag = read_tag(&song);
+    assert_eq!(tag.pictures().count(), 0);
+
+    embed_image_from_memory(&song, &image::open(&*image).unwrap()).unwrap();
+
+    let tag = read_tag(&song);
+    assert!(tag.pictures().count() > 0);
+}
+
+#[test]
+fn test_successful_png_image_embedding_and_extracting() {
+    let song = Fixture::copy("attempt_1_no_image.mp3");
+    let image = Fixture::copy("attempt_1.png");
+
+    let tag = read_tag(&song);
+    assert_eq!(tag.pictures().count(), 0);
+
+    extract_first_image_as_img(&song).unwrap_err();
+
+    embed_image(&song, &image).unwrap();
+
+    let tag = read_tag(&song);
+    assert!(tag.pictures().count() > 0);
+
+    extract_first_image_as_img(&song).unwrap();
+}
+
 #[test]
 fn test_successful_image_embedding_in_a_file_that_already_has_an_image() {
     let song = Fixture::copy("attempt_1.mp3");
@@ -125,7 +159,7 @@ fn test_removing_and_adding_an_image() {
     remove_images(&song).unwrap();
 
     let tag = read_tag(&song);
-    assert!(tag.pictures().count() == 0);
+    assert_eq!(tag.pictures().count(), 0);
 
     embed_image(&song, &image).unwrap();
 
@@ -141,7 +175,7 @@ fn test_removing_and_adding_an_image_to_a_broken_file() {
     remove_images(&song).unwrap();
 
     let tag = read_tag(&song);
-    assert!(tag.pictures().count() == 0);
+    assert_eq!(tag.pictures().count(), 0);
 
     embed_image(&song, &image).unwrap();
 
@@ -207,7 +241,7 @@ fn test_extracting_an_image_with_no_pictures() {
     let image = Fixture::blank("attempt_1.jpg");
 
     let tag = read_tag(&song);
-    assert!(tag.pictures().count() == 0);
+    assert_eq!(tag.pictures().count(), 0);
     assert!(!image.exists());
 
     assert!(extract_first_image(&song, &image).is_err());