fix: bound large WebP lossless probe cost

src/services/compress.rs

@@ -38,6 +38,7 @@ const WEBP_TARGET_MAX_QUALITY: u8 = 100;
 const AVIF_TARGET_MAX_QUALITY: u8 = 100;
 const AVIF_ENCODER_SPEED: u8 = 5;
 const WEBP_TARGET_SAFETY_PERCENT: u64 = 97;
+const WEBP_HIGH_EFFORT_LOSSLESS_MAX_PIXELS: u64 = 2_100_000;
 const METADATA_TARGET_OVERHEAD: u64 = 1024;
 
 #[derive(Clone)]
@@ -1009,7 +1010,7 @@ fn encode_webp_lossless_pixels(pixels: &TargetPixels) -> Result<Vec<u8>, AppErro
         .map_err(|_| AppError::new(ErrorCode::CompressionFailed, "初始化 WebP 无损配置失败"))?;
     config.lossless = 1;
     config.quality = 100.0;
-    config.method = 6;
+    config.method = webp_lossless_method(pixels);
     config.alpha_compression = 1;
     config.near_lossless = 100;
     config.exact = 1;
@@ -1026,6 +1027,15 @@ fn encode_webp_lossless_pixels(pixels: &TargetPixels) -> Result<Vec<u8>, AppErro
         })
 }
 
+fn webp_lossless_method(pixels: &TargetPixels) -> i32 {
+    let pixel_count = u64::from(pixels.width).saturating_mul(u64::from(pixels.height));
+    if pixel_count <= WEBP_HIGH_EFFORT_LOSSLESS_MAX_PIXELS {
+        6
+    } else {
+        0
+    }
+}
+
 fn encode_avif_target(
     image: DynamicImage,
     target_size: u64,
@@ -2035,6 +2045,25 @@ mod tests {
         assert_eq!(output, max_lossy);
     }
 
+    #[test]
+    fn large_webp_targets_use_the_fast_lossless_probe() {
+        let small = TargetPixels {
+            bytes: Vec::new(),
+            width: 1920,
+            height: 1080,
+            layout: TargetPixelLayout::Rgb,
+        };
+        let large = TargetPixels {
+            bytes: Vec::new(),
+            width: 4096,
+            height: 3072,
+            layout: TargetPixelLayout::Rgb,
+        };
+
+        assert_eq!(webp_lossless_method(&small), 6);
+        assert_eq!(webp_lossless_method(&large), 0);
+    }
+
     #[test]
     fn jpeg_target_encoder_prefers_perceptual_downscaling() {
         let image = DynamicImage::ImageRgb8(RgbImage::from_fn(800, 600, |x, y| {