Centralize prompt image detail modes (#42624)

## What changed

- Add `PromptImageMode::HIGH_DETAIL` and `PromptImageMode::ORIGINAL_DETAIL`
  constants with the standard resize limits.
- Use the shared modes during core image preparation instead of defining the
  limits locally.
- Cover the dimension and patch budgets for both detail modes in the image
  utility tests.

GitOrigin-RevId: 27fdc77719f23d2e8f1060886576b3be843a8491

codex-rs/core/src/image_preparation.rs

@@ -19,7 +19,6 @@ use codex_protocol::models::ResponseItem;
 use codex_protocol::openai_models::ModelInfo;
 use codex_utils_image::ImageProcessingError;
 use codex_utils_image::PromptImageMode;
-use codex_utils_image::PromptImageResizeLimits;
 use codex_utils_image::load_data_url_for_prompt;
 use tracing::warn;
 
@@ -31,15 +30,6 @@ const UNSUPPORTED_LOW_DETAIL_PLACEHOLDER: &str = "image content omitted because
 const REMOTE_IMAGE_URL_PLACEHOLDER: &str =
     "image content omitted because remote image URLs are not supported";
 
-const HIGH_DETAIL_LIMITS: PromptImageResizeLimits = PromptImageResizeLimits {
-    max_dimension: 2048,
-    max_patches: 2_500,
-};
-const UNIFIED_IMAGE_LIMITS: PromptImageResizeLimits = PromptImageResizeLimits {
-    max_dimension: 6000,
-    max_patches: 10_000,
-};
-
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub(crate) enum ImagePreparationMode {
     DetailBased,
@@ -288,17 +278,23 @@ fn prepare_image(
         return Ok(None);
     }
 
-    let (effective_detail, limits) = match mode {
-        ImagePreparationMode::UnifiedBudget => (ImageDetailSetting::Original, UNIFIED_IMAGE_LIMITS),
+    let (effective_detail, image_mode) = match mode {
+        ImagePreparationMode::UnifiedBudget => (
+            ImageDetailSetting::Original,
+            PromptImageMode::ORIGINAL_DETAIL,
+        ),
         ImagePreparationMode::DetailBased => match detail {
             None | Some(ImageDetail::Auto | ImageDetail::High) => {
-                (ImageDetailSetting::High, HIGH_DETAIL_LIMITS)
+                (ImageDetailSetting::High, PromptImageMode::HIGH_DETAIL)
             }
-            Some(ImageDetail::Original) => (ImageDetailSetting::Original, UNIFIED_IMAGE_LIMITS),
+            Some(ImageDetail::Original) => (
+                ImageDetailSetting::Original,
+                PromptImageMode::ORIGINAL_DETAIL,
+            ),
             Some(ImageDetail::Low) => return Err(ImagePreparationError::UnsupportedLowDetail),
         },
     };
-    let image = load_data_url_for_prompt(image_url, PromptImageMode::ResizeWithLimits(limits))?;
+    let image = load_data_url_for_prompt(image_url, image_mode)?;
     metadata.push(ImagePreparationMetadata {
         message_role: origin.message_role.map(str::to_string),
         item_id: origin.item_id.map(str::to_string),

codex-rs/utils/image/src/image_tests.rs

@@ -276,31 +276,37 @@ fn data_url_processing_rejects_malformed_input() {
     }
 }
 
+/// The shared detail modes apply the policies used by external byte-oriented callers.
 #[tokio::test(flavor = "multi_thread")]
-async fn resize_with_limits_respects_dimension_and_patch_budgets() {
-    let image = ImageBuffer::from_pixel(2048, 2048, Rgba([200u8, 10, 10, 255]));
-    let original_bytes = image_bytes(&image, ImageFormat::Png);
-    let limits = PromptImageResizeLimits {
-        max_dimension: 2048,
-        max_patches: 2_500,
-    };
+async fn detail_modes_apply_expected_budgets() {
+    for (mode, input_dimensions, expected_dimensions) in [
+        (PromptImageMode::HIGH_DETAIL, (2048, 2048), (1600, 1600)),
+        (PromptImageMode::ORIGINAL_DETAIL, (6401, 100), (6000, 94)),
+    ] {
+        let image = ImageBuffer::from_pixel(
+            input_dimensions.0,
+            input_dimensions.1,
+            Rgba([200u8, 10, 10, 255]),
+        );
+        let original_bytes = image_bytes(&image, ImageFormat::Png);
+        let processed = load_for_prompt_bytes(Path::new("in-memory-image"), original_bytes, mode)
+            .expect("process image with detail mode");
 
-    let processed = load_for_prompt_bytes(
-        Path::new("in-memory-image"),
-        original_bytes,
-        PromptImageMode::ResizeWithLimits(limits),
-    )
-    .expect("process image with explicit limits");
-
-    assert_eq!(
-        (
-            processed.source_width,
-            processed.source_height,
-            processed.width,
-            processed.height,
-        ),
-        (2048, 2048, 1600, 1600)
-    );
+        assert_eq!(
+            (
+                processed.source_width,
+                processed.source_height,
+                processed.width,
+                processed.height,
+            ),
+            (
+                input_dimensions.0,
+                input_dimensions.1,
+                expected_dimensions.0,
+                expected_dimensions.1,
+            )
+        );
+    }
 }
 
 #[tokio::test(flavor = "multi_thread")]

codex-rs/utils/image/src/lib.rs

@@ -70,6 +70,19 @@ pub struct PromptImageResizeLimits {
     pub max_patches: usize,
 }
 
+impl PromptImageMode {
+    /// Resize policy for high-detail prompt images.
+    pub const HIGH_DETAIL: Self = Self::ResizeWithLimits(PromptImageResizeLimits {
+        max_dimension: 2048,
+        max_patches: 2_500,
+    });
+    /// Resize policy for original-detail prompt images.
+    pub const ORIGINAL_DETAIL: Self = Self::ResizeWithLimits(PromptImageResizeLimits {
+        max_dimension: 6000,
+        max_patches: 10_000,
+    });
+}
+
 struct ImageMetadata {
     icc_profile: Option<Vec<u8>>,
     exif: Option<Vec<u8>>,