Image Format Converter

What is Image Format Converter?

An Image Format Converter transforms image files between JPG (JPEG) and PNG formats. JPG (Joint Photographic Experts Group) uses lossy compression ideal for photographs with millions of colors, producing small file sizes. PNG (Portable Network Graphics) uses lossless compression and supports full transparency, making it suited for graphics, logos, and images with sharp edges. This converter supports bidirectional conversion between the two formats entirely in your browser.

How It Works

For JPG to PNG, the tool reads the uploaded JPG file via the FileReader API, decodes it into an HTMLImageElement, draws it onto a Canvas at native dimensions, and exports the canvas as a PNG blob using toBlob with image/png MIME type. For PNG to JPG, the same pipeline is used but the canvas is first filled with a white background (since JPG does not support transparency) before drawing the image, then exported with image/jpeg at 92% quality. All processing is local and private.

Common Use Cases

• Converting photographs from JPG to PNG for lossless editing
• Preparing images with transparency for use on websites by converting from JPG to PNG
• Reducing file size of PNG graphics by converting to JPG when transparency is not needed
• Standardizing image formats across a batch of mixed JPG and PNG files
• Preparing images for upload to platforms that only accept a specific format

Technical Details

The converter uses FileReader.readAsDataURL to load the image, Image.decode() for async decoding, an offscreen Canvas with 2D context for rasterization, and canvas.toBlob() for encoding. PNG output uses lossless encoding (no quality parameter). JPG output uses 92% quality with white background fill for transparent regions. Object URLs are revoked after use to prevent memory leaks. The converter runs entirely in the browser with no network requests.