From 2b3fc13febb41752e9ea04b607d45b66cd85f824 Mon Sep 17 00:00:00 2001
From: Nishit24113 <npate230@asu.edu>
Date: Wed, 29 Apr 2026 13:53:03 -0700
Subject: [PATCH] Fix Bedrock aspect ratio rejection for form PDFs

---
 .../alt_text_generator.js                     | 60 +++++++++++++++++--
 1 file changed, 54 insertions(+), 6 deletions(-)

diff --git a/alt-text-generator-container/alt_text_generator.js b/alt-text-generator-container/alt_text_generator.js
index 05e39a98..eecd3a75 100644
--- a/alt-text-generator-container/alt_text_generator.js
+++ b/alt-text-generator-container/alt_text_generator.js
@@ -69,6 +69,42 @@ function sleep(ms) {
     return new Promise(resolve => setTimeout(resolve, ms));
 }
 
+const MAX_ASPECT_RATIO = 20;
+
+function getImageDimensions(buffer) {
+    try {
+        if (buffer[0] === 0x89 && buffer[1] === 0x50 && buffer[2] === 0x4E && buffer[3] === 0x47) {
+            const width = buffer.readUInt32BE(16);
+            const height = buffer.readUInt32BE(20);
+            return { width, height };
+        }
+        if (buffer[0] === 0xFF && buffer[1] === 0xD8) {
+            let offset = 2;
+            while (offset < buffer.length - 1) {
+                if (buffer[offset] !== 0xFF) break;
+                const marker = buffer[offset + 1];
+                if (marker === 0xC0 || marker === 0xC2) {
+                    const height = buffer.readUInt16BE(offset + 5);
+                    const width = buffer.readUInt16BE(offset + 7);
+                    return { width, height };
+                }
+                const segmentLength = buffer.readUInt16BE(offset + 2);
+                offset += 2 + segmentLength;
+            }
+        }
+        return null;
+    } catch (e) {
+        return null;
+    }
+}
+
+function isAspectRatioValid(dimensions) {
+    if (!dimensions || !dimensions.width || !dimensions.height) return true;
+    const { width, height } = dimensions;
+    const ratio = Math.max(width / height, height / width);
+    return ratio <= MAX_ASPECT_RATIO;
+}
+
 
 /**
  * Invokes the Bedrock AI model to generate alt text for a given image.
@@ -492,6 +528,8 @@ async function startProcess() {
         logger.info(`Filename: ${filebasename} | imageObjects: ${imageObjects}`);
         logger.info(`Filename: ${filebasename} | Total images to process: ${imageObjects.length}`);
         
+        let skippedCount = 0;
+
         for (const imageObject of imageObjects) {
             try {
                 const getObjectParams = {
@@ -502,7 +540,7 @@ async function startProcess() {
                 logger.info(`Filename: ${filebasename} | Image Object Bucketname: ${bucketName}`);
                 const command = new GetObjectCommand(getObjectParams);
                 const { Body } = await s3Client.send(command);
-        
+
                 // Stream the body contents to a buffer
                 const chunks = [];
                 await pipeline(Body, async function* (source) {
@@ -511,6 +549,16 @@ async function startProcess() {
                     }
                 });
                 const fileBuffer = Buffer.concat(chunks);
+
+                const dimensions = getImageDimensions(fileBuffer);
+                if (dimensions && !isAspectRatioValid(dimensions)) {
+                    skippedCount++;
+                    const altText = "Decorative element";
+                    combinedResults[imageObject.id] = altText;
+                    logger.info(`Filename: ${filebasename} | Skipping image ${imageObject.id} - aspect ratio ${Math.max(dimensions.width/dimensions.height, dimensions.height/dimensions.width).toFixed(1)}:1 exceeds ${MAX_ASPECT_RATIO}:1 limit (${dimensions.width}x${dimensions.height})`);
+                    continue;
+                }
+
                 const localFilePath = path.join(__dirname, `${imageObject.path.split('/').pop()}`);
                 logger.info(`Filename: ${filebasename} | Local File Path: ${localFilePath}`);
                 fs_1.writeFileSync(localFilePath, fileBuffer);
@@ -519,23 +567,23 @@ async function startProcess() {
                 logger.info(`Filename: ${filebasename} | Response:${response}`);
                 Object.assign(combinedResults, JSON.parse(response));
                 successCount++;
-                logger.info(`Filename: ${filebasename} | Alt text generation succeeded for image ${imageObject.id} (${successCount} succeeded, ${failureCount} failed)`);
+                logger.info(`Filename: ${filebasename} | Alt text generation succeeded for image ${imageObject.id} (${successCount} succeeded, ${failureCount} failed, ${skippedCount} skipped)`);
             } catch (error) {
                 failureCount++;
                 logger.error(`Filename: ${filebasename} | Alt text generation failed for image ${imageObject.id}: ${error.message || error}`);
-                logger.info(`Filename: ${filebasename} | Progress: ${successCount} succeeded, ${failureCount} failed`);
+                logger.info(`Filename: ${filebasename} | Progress: ${successCount} succeeded, ${failureCount} failed, ${skippedCount} skipped`);
             }
             await sleep(2000);
         }
 
-        // Check if we have any images and if all of them failed
-        if (imageObjects.length > 0 && successCount === 0) {
+        // Only fail if all images failed AND none were skipped (skipped images got default alt text)
+        if (imageObjects.length > 0 && successCount === 0 && skippedCount === 0) {
             logger.error(`Filename: ${filebasename} | All ${failureCount} alt text generation requests failed - likely due to throttling or Bedrock API issues`);
             logger.error(`File: ${filebasename}, Status: Failed in second ECS task - All Bedrock requests failed`);
             process.exit(1);
         }
         
-        logger.info(`Filename: ${filebasename} | Alt text generation complete: ${successCount} succeeded, ${failureCount} failed out of ${imageObjects.length} images`);
+        logger.info(`Filename: ${filebasename} | Alt text generation complete: ${successCount} succeeded, ${failureCount} failed, ${skippedCount} skipped (bad aspect ratio) out of ${imageObjects.length} images`);
 
         let defaultText = "No text available";