Merge pull request #35333 from overleaf/bg-png2pdf-minimum-size-threshold

enforce a minimum size threshold on png2pdf conversions

GitOrigin-RevId: fa558afb5455ff5d0373e3d50e57f7207a923fcb

services/clsi/app/js/HistoryResourceWriter.js

@@ -38,6 +38,16 @@ function isPng(path) {
   return Path.extname(path).toLowerCase() === '.png'
 }
 
+/**
+ * Returns true if the PNG file size (bytes) is below the conversion threshold
+ * @param {number} fileSize
+ * @returns {boolean}
+ */
+
+function pngBelowSizeThreshold(fileSize) {
+  return fileSize < Settings.png2pdfMinFileSizeBytes
+}
+
 export const clearCacheCb = callbackify(clearCache)
 
 /**
@@ -561,6 +571,7 @@ export async function syncResourcesToDisk(
           'utf-8'
         )
       } else {
+        const fileSize = file.getByteLength() || 0
         const hash = file.getHash()
         if (!hash) {
           throw new OError('unexpected file without content and hash', { path })
@@ -574,7 +585,16 @@ export async function syncResourcesToDisk(
         try {
           const fallbackURL = null // no fallback
           const lastModified = new Date(0) // content is static
-          if (request.png2pdf && Png2Pdf.isEnabled() && isPng(path)) {
+          const isConvertiblePng =
+            request.png2pdf && Png2Pdf.isEnabled() && isPng(path)
+          // Avoid doing unnecessary work converting small PNGs
+          const skipConversion =
+            isConvertiblePng && pngBelowSizeThreshold(fileSize)
+          if (skipConversion) {
+            Metrics.inc('png2pdf-skipped-small')
+          }
+          // Take the conversion path for PNGs to be optimised
+          if (isConvertiblePng && !skipConversion) {
             // PNG files go through a batch conversion process first.
             const toConvert = await UrlCache.promises.downloadUrlToFile(
               projectId,

services/clsi/config/settings.defaults.cjs

@@ -37,6 +37,8 @@ module.exports = {
   png2pdfImage:
     process.env.PNG2PDF_IMAGE || 'quay.io/sharelatex/png2pdf:2026-06-24',
   enablePng2pdfConversions: process.env.ENABLE_PNG2PDF_CONVERSIONS === 'true',
+  png2pdfMinFileSizeBytes:
+    parseInt(process.env.PNG2PDF_MIN_FILE_SIZE_BYTES, 10) || 1024 * 1024,
   maxUploadSize: 50 * 1024 * 1024,
   preciousFilePattern: process.env.PRECIOUS_FILE_PATTERN || '',