fix(ui): performance improvements in the bulk uploader when adding lots of images at once

packages/ui/src/elements/BulkUpload/FileSidebar/index.tsx

@@ -36,6 +36,7 @@ export function FileSidebar() {
     isInitializing,
     removeFile,
     setActiveIndex,
+    thumbnailUrls,
     totalErrorCount,
   } = useFormsManager()
   const { initialFiles, maxFiles } = useBulkUpload()
@@ -148,9 +149,7 @@ export function FileSidebar() {
                   >
                     <Thumbnail
                       className={`${baseClass}__thumbnail`}
-                      fileSrc={
-                        isImage(currentFile.type) ? URL.createObjectURL(currentFile) : undefined
-                      }
+                      fileSrc={isImage(currentFile.type) ? thumbnailUrls[index] : undefined}
                     />
                     <div className={`${baseClass}__fileDetails`}>
                       <p className={`${baseClass}__fileName`} title={currentFile.name}>

packages/ui/src/elements/BulkUpload/FormsManager/index.tsx

@@ -16,6 +16,7 @@ import { useTranslation } from '../../../providers/Translation/index.js'
 import { getFormState } from '../../../utilities/getFormState.js'
 import { hasSavePermission as getHasSavePermission } from '../../../utilities/hasSavePermission.js'
 import { useLoadingOverlay } from '../../LoadingOverlay/index.js'
+import { createThumbnail } from '../../Thumbnail/createThumbnail.js'
 import { useBulkUpload } from '../index.js'
 import { createFormData } from './createFormData.js'
 import { formsManagementReducer } from './reducer.js'
@@ -41,6 +42,7 @@ type FormsManagerContext = {
     errorCount: number
     index: number
   }) => void
+  readonly thumbnailUrls: string[]
   readonly totalErrorCount?: number
 }
 
@@ -59,6 +61,7 @@ const Context = React.createContext<FormsManagerContext>({
   saveAllDocs: () => Promise.resolve(),
   setActiveIndex: () => 0,
   setFormTotalErrorCount: () => {},
+  thumbnailUrls: [],
   totalErrorCount: 0,
 })
 
@@ -90,6 +93,40 @@ export function FormsManagerProvider({ children }: FormsManagerProps) {
   const [state, dispatch] = React.useReducer(formsManagementReducer, initialState)
   const { activeIndex, forms, totalErrorCount } = state
 
+  const formsRef = React.useRef(forms)
+  formsRef.current = forms
+  const formsCount = forms.length
+
+  const thumbnailUrlsRef = React.useRef<string[]>([])
+  const processedFiles = React.useRef(new Set()) // Track already-processed files
+  const [renderedThumbnails, setRenderedThumbnails] = React.useState<string[]>([])
+
+  React.useEffect(() => {
+    // eslint-disable-next-line @typescript-eslint/no-floating-promises
+    ;(async () => {
+      const newThumbnails = [...thumbnailUrlsRef.current]
+
+      for (let i = 0; i < formsCount; i++) {
+        const file = formsRef.current[i].formState.file.value as File
+
+        // Skip if already processed
+        if (processedFiles.current.has(file) || !file) {
+          continue
+        }
+        processedFiles.current.add(file)
+
+        // Generate thumbnail and update ref
+        const thumbnailUrl = await createThumbnail(file)
+        newThumbnails[i] = thumbnailUrl
+        thumbnailUrlsRef.current = newThumbnails
+
+        // Trigger re-render in batches
+        setRenderedThumbnails([...newThumbnails])
+        await new Promise((resolve) => setTimeout(resolve, 100))
+      }
+    })()
+  }, [formsCount, createThumbnail])
+
   const { toggleLoadingOverlay } = useLoadingOverlay()
   const { closeModal } = useModal()
   const { collectionSlug, drawerSlug, initialFiles, onSuccess } = useBulkUpload()
@@ -378,6 +415,7 @@ export function FormsManagerProvider({ children }: FormsManagerProps) {
         saveAllDocs,
         setActiveIndex,
         setFormTotalErrorCount,
+        thumbnailUrls: renderedThumbnails,
         totalErrorCount,
       }}
     >

packages/ui/src/elements/Thumbnail/createThumbnail.ts

@@ -0,0 +1,52 @@
+/**
+ * Create a thumbnail from a File object by drawing it onto an OffscreenCanvas
+ */
+export const createThumbnail = (file: File): Promise<string> => {
+  return new Promise((resolve, reject) => {
+    const img = new Image()
+    img.src = URL.createObjectURL(file) // Use Object URL directly
+
+    img.onload = () => {
+      const maxDimension = 280
+      let drawHeight: number, drawWidth: number
+
+      // Calculate aspect ratio
+      const aspectRatio = img.width / img.height
+
+      // Determine dimensions to fit within maxDimension while maintaining aspect ratio
+      if (aspectRatio > 1) {
+        // Image is wider than tall
+        drawWidth = maxDimension
+        drawHeight = maxDimension / aspectRatio
+      } else {
+        // Image is taller than wide, or square
+        drawWidth = maxDimension * aspectRatio
+        drawHeight = maxDimension
+      }
+
+      const canvas = new OffscreenCanvas(drawWidth, drawHeight) // Create an OffscreenCanvas
+      const ctx = canvas.getContext('2d')
+
+      // Draw the image onto the OffscreenCanvas with calculated dimensions
+      ctx.drawImage(img, 0, 0, drawWidth, drawHeight)
+
+      // Convert the OffscreenCanvas to a Blob and free up memory
+      canvas
+        .convertToBlob({ type: 'image/jpeg', quality: 0.25 })
+        .then((blob) => {
+          URL.revokeObjectURL(img.src) // Release the Object URL
+          const reader = new FileReader()
+          reader.onload = () => resolve(reader.result as string) // Resolve as data URL
+          reader.onerror = reject
+          reader.readAsDataURL(blob)
+        })
+        .catch(reject)
+    }
+
+    img.onerror = (error) => {
+      URL.revokeObjectURL(img.src) // Release Object URL on error
+      // eslint-disable-next-line @typescript-eslint/prefer-promise-reject-errors
+      reject(error)
+    }
+  })
+}

packages/ui/src/elements/Thumbnail/index.tsx

@@ -8,6 +8,7 @@ const baseClass = 'thumbnail'
 import type { SanitizedCollectionConfig } from 'payload'
 
 import { File } from '../../graphics/File/index.js'
+import { useIntersect } from '../../hooks/useIntersect.js'
 import { ShimmerEffect } from '../ShimmerEffect/index.js'
 
 export type ThumbnailProps = {
@@ -28,6 +29,7 @@ export const Thumbnail: React.FC<ThumbnailProps> = (props) => {
 
   React.useEffect(() => {
     if (!fileSrc) {
+      // eslint-disable-next-line @eslint-react/hooks-extra/no-direct-set-state-in-use-effect
       setFileExists(false)
       return
     }
@@ -72,6 +74,7 @@ export function ThumbnailComponent(props: ThumbnailComponentProps) {
 
   React.useEffect(() => {
     if (!fileSrc) {
+      // eslint-disable-next-line @eslint-react/hooks-extra/no-direct-set-state-in-use-effect
       setFileExists(false)
       return
     }