feat: Don't scale down huge non-JPEGs, recode them first (#7977)

If after recoding to JPEG the image isn't huge anymore, don't scale it down, this preserves quality
of most screenshots. For JPEGs however we don't try to recode them w/o scaling down:
- They are already JPEG-encoded, maybe with higher quality, but anyway.
- We don't want extra CPU work for most photos.

Author: iequidoo

src/blob.rs

@@ -419,6 +419,17 @@ impl<'a> BlobObject<'a> {
             // also `Viewtype::Gif` (maybe renamed to `Animation`) should be used for animated
             // images.
             let do_scale = exceeds_max_bytes
+                // Don't recode huge JPEGs w/o resizing:
+                // - It may be huge because of high JPEG quality, but we don't know that.
+                // - We don't want extra CPU work for most photos.
+                && (fmt == ImageFormat::Jpeg
+                    || encoded_img_exceeds_bytes(
+                        context,
+                        &img,
+                        ofmt.clone(),
+                        max_bytes,
+                        &mut encoded,
+                    )?)
                 || is_avatar
                     && (exceeds_wh
                         || exif.is_some() && {
@@ -480,8 +491,7 @@ impl<'a> BlobObject<'a> {
                     }
                 }
             }
-
-            if do_scale || exif.is_some() {
+            if !encoded.is_empty() || exif.is_some() {
                 // The file format is JPEG/PNG now, we may have to change the file extension
                 if !matches!(fmt, ImageFormat::Jpeg)
                     && matches!(ofmt, ImageOutputFormat::Jpeg { .. })

src/blob/blob_tests.rs

@@ -440,6 +440,26 @@ async fn test_recode_image_balanced_png() {
     .unwrap();
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_recode_image_balanced_png_huge() {
+    let bytes = include_bytes!("../../test-data/image/screenshot-huge.png");
+
+    SendImageCheckMediaquality {
+        viewtype: Viewtype::Image,
+        media_quality_config: "0",
+        bytes,
+        extension: "jpg",
+        original_width: 1618,
+        original_height: 949,
+        compressed_width: 1618,
+        compressed_height: 949,
+        ..Default::default()
+    }
+    .test()
+    .await
+    .unwrap();
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_sticker_with_exif() {
     let bytes = include_bytes!("../../test-data/image/logo-exif.png");