JPEG images are already compressed; any attempt to compress further with Zip, LHA or other tool rarely is of use. There are two ways to reduce the file size, both of which can be applied at the same time:
- Reduce the image size, e.g. scale down from 1024×768 to 800×600 pixels.
- Reduce the image quality. JPEG uses a lossy but fast compression scheme. If an image is saved at a lower JPEG quality setting, the file size is reduced, albeit with some loss of detail.
There are a number of free tools for different platforms such as GIMP (Linux, Windows etc.) and IrfanView (Windows, but works well in Wine) that can perform both operations on the image. Though you may need to experiment initially to find settings you find pleasing, you can standardize on those.
Images often account for most of the downloaded bytes on a web page and also often occupy a significant amount of visual space. As a result, optimizing images can often yield some of the largest byte savings and performance improvements for your website: the fewer bytes the browser has to download, the less competition there is for the client’s bandwidth and the faster the browser can download and render useful content on the screen.
Image optimization is both an art and science: an art because there is no one definitive answer for how best to compress an individual image, and a science because there are many well developed techniques and algorithms that can significantly reduce the size of an image. Finding the optimal settings for your image requires careful analysis along many dimensions: format capabilities, content of encoded data, quality, pixel dimensions, and more.
- Adobe Photoshop
Save For Web: Better JPEG Compression with Adobe Photoshop Blog
RIOT (Radical Image Optimization Tool) is a free program to optimize images for the web efficiently. It includes an easy-to-use interface to compare the original with the optimized image in real time, so you can instantly see the resulting file size.The program is lightweight, fast and boasts powerful features for more advanced users. It supports various formats and features automatic optimization that selects the most suitable format and parameters.Price: Free
- Adobe Photoshop