How to Convert Image Formats

Problem

You have an image in one format and need it in another for a specific use case or platform.

Prerequisites

• Understanding of image formats
• Knowledge of format limitations

Steps

1. 1. Understand format capabilities

   PNG supports transparency and lossless compression. JPEG does not support transparency and uses lossy compression. WebP supports both transparency and lossy/lossless. GIF supports animation but limited colors (256). Choose the target format based on your needs.

   Input

   need: transparency + small size

   Output

   target: WebP

2. 2. Convert the image

   Load the source image and encode it in the target format. For JPEG, set quality (typically 80-90). For PNG, choose compression level. For WebP, choose lossy or lossless. The conversion happens entirely in the browser using the Canvas API or WebAssembly.

   Input

   PNG → WebP (quality 85)

   Output

   WebP image

3. 3. Verify quality and size

   Compare the converted image with the original. Check that transparency is preserved if the target supports it. Compare file sizes. If the target format does not support a feature (e.g., JPEG does not support transparency), decide how to handle it (e.g., composite onto white).

   Input

   converted image

   Output

   quality verified, size reduced

Expected result

The image converted to the target format with appropriate quality and features.

Common errors

Transparency lost converting to JPEG

JPEG does not support transparency. Use PNG or WebP instead, or composite the image onto a background color before converting.

Colors changed converting to GIF

GIF supports only 256 colors. For photos, use PNG or WebP. For simple graphics, GIF may be acceptable.

Troubleshooting

• If quality is poor, increase the quality setting for lossy formats.
• If the file is larger, the target format may be less efficient for this image type.

Security limits

• Image conversion is a local operation. No image data leaves your browser.