Alternative text labels aren’t visible onscreen, but they let page readers audibly describe what's onscreen, making navigation easier for people with visual impairments. Provide alternative text labels for images and icons. However, transparency is necessary in complication images, menu icons, and other glyphs that serve as template images and are tinted programmatically. If an image will always be composited on the same, solid background colour, it's more efficient to include the background in the image. Images with transparency include an alpha channel, which increases file size. Experiment with compression settings on each image to find the optimal value that yields an acceptable result. Even a small amount of compression can save significant disk space. Most JPEG files can be compressed without noticeable degradation of the resulting image. Optimize JPEG files to find a balance between size and quality. This palette is not appropriate for photos. Using an 8-bit colour palette reduces file size without reducing image quality. Use the 8-bit colour palette for PNG graphics that don’t require full 24-bit colour. Photo-realistic app icons, however, look best as PNGs. Its compression algorithm usually produces smaller sizes than lossless formats and artefacts are harder to discern in photos. It's a good choice for intricate artwork that requires effects like shading, textures, and highlights.

PNG supports transparency and, because it's lossless, compression artefacts don't blur important details or alter colours. In general, use de-interlaced PNG files for bitmap/raster artwork. What format to use Produce artwork in the appropriate format. Think about the needs of your site and how you might design your image files to be as small as possible while achieving optimal performance and maintaining the visual style you want. Why do we need to optimize images? Optimizing your website’s images improves performance.

Gimp gif labeling