修复图片改造后二维清晰度降级问题

前端按图层真实尺寸恢复图片改造比例与清晰度

后端在角色去背景后恢复生成原图像素尺寸

补充前后端二千像素尺寸回归测试

同步更新图片画布技术文档与项目决策记录

server-rs/crates/api-server/src/editor_project.rs

@@ -1852,11 +1852,28 @@ pub(crate) async fn generate_editor_image_for_owner(
                 ));
             }
         };
-        image = removal.image;
+        let removal_provider = removal.provider;
+        let (restored_removal_image, postprocess_dimension_error) =
+            restore_editor_postprocessed_image_output_dimensions_or_original(
+                removal.image,
+                provider_width,
+                provider_height,
+            );
+        if let Some(error) = postprocess_dimension_error {
+            tracing::warn!(
+                task_id = %generated.task_id,
+                provider = removal_provider,
+                provider_width,
+                provider_height,
+                error = ?error,
+                "角色透明图尺寸恢复失败，保留去背景服务原始输出"
+            );
+        }
+        image = restored_removal_image;
         output_prompt = "去除纯色背景".to_string();
         output_actual_prompt = None;
         output_model = removal.model;
-        output_provider = removal.provider.to_string();
+        output_provider = removal_provider.to_string();
         output_generation_inputs =
             build_editor_derived_asset_generation_inputs("角色抠图", &output_model, &source_record);
         Some(source_record)
@@ -2418,9 +2435,10 @@ async fn ensure_editor_image_edit_source_allowed(
     ensure_editor_image_edit_asset_kind_allowed(asset_kind)
 }
 
-fn encode_editor_image_edit_png(
+fn encode_editor_image_png(
     image: image::DynamicImage,
     failure_status: StatusCode,
+    provider: &str,
     failure_message: &str,
 ) -> Result<Vec<u8>, AppError> {
     let mut bytes = Cursor::new(Vec::new());
@@ -2428,13 +2446,21 @@ fn encode_editor_image_edit_png(
         .write_to(&mut bytes, image::ImageFormat::Png)
         .map_err(|error| {
             AppError::from_status(failure_status).with_details(json!({
-                "provider": "editor-image-edit",
+                "provider": provider,
                 "message": format!("{failure_message}：{error}"),
             }))
         })?;
     Ok(bytes.into_inner())
 }
 
+fn encode_editor_image_edit_png(
+    image: image::DynamicImage,
+    failure_status: StatusCode,
+    failure_message: &str,
+) -> Result<Vec<u8>, AppError> {
+    encode_editor_image_png(image, failure_status, "editor-image-edit", failure_message)
+}
+
 fn prepare_editor_image_edit_references(
     reference_images: &mut [OpenAiReferenceImage],
     target_size: &str,
@@ -2571,6 +2597,51 @@ fn restore_editor_generated_image_output_dimensions_or_original(
     }
 }
 
+fn restore_editor_postprocessed_image_output_dimensions(
+    output: &DownloadedOpenAiImage,
+    target_width: u32,
+    target_height: u32,
+) -> Result<Option<DownloadedOpenAiImage>, AppError> {
+    let decoded = image::load_from_memory(output.bytes.as_slice()).map_err(|error| {
+        AppError::from_status(StatusCode::BAD_GATEWAY).with_details(json!({
+            "provider": "editor-character-image",
+            "message": format!("角色透明图不是有效图片：{error}"),
+        }))
+    })?;
+    if decoded.width() == target_width && decoded.height() == target_height {
+        return Ok(None);
+    }
+
+    let restored = decoded.resize_exact(
+        target_width,
+        target_height,
+        image::imageops::FilterType::Lanczos3,
+    );
+    Ok(Some(DownloadedOpenAiImage {
+        bytes: encode_editor_image_png(
+            restored,
+            StatusCode::BAD_GATEWAY,
+            "editor-character-image",
+            "恢复角色透明图尺寸失败",
+        )?,
+        mime_type: "image/png".to_string(),
+        extension: "png".to_string(),
+    }))
+}
+
+fn restore_editor_postprocessed_image_output_dimensions_or_original(
+    output: DownloadedOpenAiImage,
+    target_width: u32,
+    target_height: u32,
+) -> (DownloadedOpenAiImage, Option<AppError>) {
+    match restore_editor_postprocessed_image_output_dimensions(&output, target_width, target_height)
+    {
+        Ok(Some(restored)) => (restored, None),
+        Ok(None) => (output, None),
+        Err(error) => (output, Some(error)),
+    }
+}
+
 fn restore_editor_generated_image_output_dimensions(
     output: &DownloadedOpenAiImage,
     model: &str,
@@ -8469,6 +8540,33 @@ mod tests {
         assert_eq!(restored.extension, "png");
     }
 
+    #[test]
+    fn character_postprocess_restores_provider_dimensions() {
+        let image = image::DynamicImage::new_rgba8(1024, 1024);
+        let mut bytes = Cursor::new(Vec::new());
+        image
+            .write_to(&mut bytes, image::ImageFormat::Png)
+            .expect("test image should encode");
+        let postprocessed = DownloadedOpenAiImage {
+            bytes: bytes.into_inner(),
+            mime_type: "image/png".to_string(),
+            extension: "png".to_string(),
+        };
+
+        let restored =
+            restore_editor_postprocessed_image_output_dimensions(&postprocessed, 2048, 2048)
+                .expect("postprocessed image should restore provider dimensions")
+                .expect("1K postprocessed image should be resized back to 2K");
+        let restored_image = image::load_from_memory(restored.bytes.as_slice()).unwrap();
+
+        assert_eq!(
+            (restored_image.width(), restored_image.height()),
+            (2048, 2048)
+        );
+        assert_eq!(restored.mime_type, "image/png");
+        assert_eq!(restored.extension, "png");
+    }
+
     #[test]
     fn publication_material_generation_restores_provider_output_to_workflow_dimensions() {
         let image = image::DynamicImage::new_rgba8(944, 704);