Create Thumbnail - Electron

Generate thumbnail preview images from CE.SDK scenes by exporting with target dimensions for galleries and design management.

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Thumbnails provide visual previews of designs without loading the full editor. Use engine.block.export() with targetWidth and targetHeight options to scale content while maintaining aspect ratio. Supported formats include PNG, JPEG, and WebP.

import type CreativeEditorSDK from '@cesdk/cesdk-js';
import type { EditorPlugin, EditorPluginContext } from '@cesdk/cesdk-js';
import packageJson from './package.json';

class Example implements EditorPlugin {
  name = packageJson.name;

  version = packageJson.version;

  async initialize({ cesdk }: EditorPluginContext): Promise<void> {
    if (!cesdk) {
      throw new Error('CE.SDK instance is required for this plugin');
    }

    const engine = cesdk.engine;

    await engine.scene.loadFromURL(
      'https://cdn.img.ly/assets/demo/v1/ly.img.template/templates/cesdk_postcard_1.scene'
    );
    const page = engine.scene.getCurrentPage();
    if (!page) throw new Error('No page found');
    await engine.scene.zoomToBlock(page, { padding: 40 });

    // Setup thumbnail export functionality
    await this.setupThumbnailActions(cesdk, page);
  }

  private async setupThumbnailActions(
    cesdk: CreativeEditorSDK,
    page: number
  ): Promise<void> {
    const engine = cesdk.engine;

    // Add thumbnail export buttons to navigation bar
    cesdk.ui.insertNavigationBarOrderComponent('last', {
      id: 'ly.img.actions.navigationBar',
      children: [
        {
          id: 'ly.img.action.navigationBar',
          key: 'export-thumbnail-small',
          label: 'Small Thumbnail',
          icon: '@imgly/Save',
          onClick: async () => {
            const blob = await engine.block.export(page, {
              mimeType: 'image/jpeg',
              targetWidth: 150,
              targetHeight: 150,
              jpegQuality: 0.8
            });

            await cesdk.utils.downloadFile(blob, 'image/jpeg');
            console.log(
              `✓ Small thumbnail: ${(blob.size / 1024).toFixed(1)} KB`
            );
          }
        },
        {
          id: 'ly.img.action.navigationBar',
          key: 'export-thumbnail-medium',
          label: 'Medium Thumbnail',
          icon: '@imgly/Save',
          onClick: async () => {
            const blob = await engine.block.export(page, {
              mimeType: 'image/jpeg',
              targetWidth: 400,
              targetHeight: 300,
              jpegQuality: 0.85
            });

            await cesdk.utils.downloadFile(blob, 'image/jpeg');
            console.log(
              `✓ Medium thumbnail: ${(blob.size / 1024).toFixed(1)} KB`
            );
          }
        },
        {
          id: 'ly.img.action.navigationBar',
          key: 'export-thumbnail-png',
          label: 'PNG Thumbnail',
          icon: '@imgly/Save',
          onClick: async () => {
            const blob = await engine.block.export(page, {
              mimeType: 'image/png',
              targetWidth: 400,
              targetHeight: 300,
              pngCompressionLevel: 6
            });

            await cesdk.utils.downloadFile(blob, 'image/png');
            console.log(`✓ PNG thumbnail: ${(blob.size / 1024).toFixed(1)} KB`);
          }
        },
        {
          id: 'ly.img.action.navigationBar',
          key: 'export-thumbnail-webp',
          label: 'WebP Thumbnail',
          icon: '@imgly/Save',
          onClick: async () => {
            const blob = await engine.block.export(page, {
              mimeType: 'image/webp',
              targetWidth: 400,
              targetHeight: 300,
              webpQuality: 0.8
            });

            await cesdk.utils.downloadFile(blob, 'image/webp');
            console.log(
              `✓ WebP thumbnail: ${(blob.size / 1024).toFixed(1)} KB`
            );
          }
        }
      ]
    });
  }
}

export default Example;

This guide covers exporting thumbnails at specific dimensions, choosing formats, optimizing quality and file size, and generating multiple thumbnail sizes.

Export a Thumbnail#

Call engine.block.export() with target dimensions to create a scaled thumbnail. Both targetWidth and targetHeight must be set together for scaling to work.

const blob = await engine.block.export(page, {
  mimeType: 'image/jpeg',
  targetWidth: 150,
  targetHeight: 150,
  jpegQuality: 0.8
});

The block renders large enough to fill the target size while maintaining aspect ratio. If aspect ratios differ, the output extends beyond the target on one axis.

Choose Thumbnail Format#

Select the format via the mimeType option based on your needs:

'image/jpeg' — Smaller files, good for photos, no transparency
'image/png' — Lossless quality, supports transparency
'image/webp' — Best compression, modern browsers only

JPEG Thumbnails#

JPEG works well for photographic content. Control file size with jpegQuality (0-1, default 0.9). Values between 0.75-0.85 balance quality and size for thumbnails.

const blob = await engine.block.export(page, {
  mimeType: 'image/jpeg',
  targetWidth: 400,
  targetHeight: 300,
  jpegQuality: 0.85
});

PNG Thumbnails#

PNG provides lossless quality with transparency support. Control encoding speed vs. file size with pngCompressionLevel (0-9, default 5).

const blob = await engine.block.export(page, {
  mimeType: 'image/png',
  targetWidth: 400,
  targetHeight: 300,
  pngCompressionLevel: 6
});

WebP Thumbnails#

WebP offers the best compression for modern browsers. Control quality with webpQuality (0-1, default 1.0 for lossless).

const blob = await engine.block.export(page, {
  mimeType: 'image/webp',
  targetWidth: 400,
  targetHeight: 300,
  webpQuality: 0.8
});

Common Thumbnail Sizes#

Standard sizes for different use cases:

Size	Dimensions	Use Case
Small	150×150	Grid galleries, file browsers
Medium	400×300	Preview panels, cards
Large	800×600	Full previews, detail views

Optimize Thumbnail Quality#

Balance quality with file size using format-specific options:

Format	Option	Range	Default	Notes
JPEG	`jpegQuality`	0-1	0.9	Lower = smaller files, visible artifacts
PNG	`pngCompressionLevel`	0-9	5	Higher = smaller files, slower encoding
WebP	`webpQuality`	0-1	1.0	1.0 = lossless, lower = lossy compression

For thumbnails, JPEG quality of 0.8 or WebP quality of 0.75-0.85 typically provides good results with small file sizes.

API Reference#

Method	Description
`engine.block.export(blockId, options)`	Export a block as image with format and dimension options
`engine.scene.getCurrentPage()`	Get the current page block ID
`cesdk.utils.downloadFile(blob, mimeType)`	Download a blob to the user’s device