- Resize the image - Larger images take up more disk space because there are more pixels and, hence more colour information that has to be stored. By shrinking the height and width of an image to the smallest they can be, you take a big step toward making the file as small as it can be.
Caution
Always resize an image in a graphics program, keeping the aspect ratio the same. If you try to use the WIDTH and HEIGHT attributes of the <IMG> tag to resize the image, you’re relying on the browser to do the resizing and you’re likely to be disappointed with the results. Additionally, resizing with the browser doesn’t save you download time because the original image file still has to be downloaded.
- Use thumbnails - Thumbnails are very small versions of an image, usually a photograph. Because they’re smaller, their file sizes are smaller, too.
Tip
Thumbnails are typically set up so that a visitor can click them to see the full image. If you do this, be sure to include the size of the full image file in parentheses next to the thumbnail so that visitors can make an informed decision about viewing it or not.
Store GIF’s as JPEG’s - JPEG compression works best on images with lots of colour graduation. If you have a GIF file that fits this description, try saving it as a JPEG to see if that makes the file any smaller.
- Increase the compression ratio - if you’re working with a JPEG, you can resave it at a higher compression ratio to shrink the file size. But don’t forget the trade-off: higher compression reduces the quality of the image.
- Reduce the colour depth - Colour depth is another way to express how many colours can be stored by a format. A GIF image has a colour depth of eight bits (256 colours) - but what if there are fewer than 256 colours in the image? In this case you can reduce the colour depth to a smaller number of bits per pixel. With less information to store per pixel, the resulting file will be smaller.
- Adjust contrast levels in the image - Contrast refers to the brightness of objects in the image relative to one another. Most popular graphics programs offer retouching options like gamma correction and highlight/midtone/shadow that change contrast within an image. By tweaking these values, you can usually bring down your file size.
- Suppress dithering - Dithering refers to the use of colours in an existing colour palette to approximate colours that are not in the palette. Dithering tends to increase file size in GIF’s because the GIF compression scheme is less efficient when adjacent pixels are painted with different colours. Disabling dithering will make more adjacent pixels have the same colour so the compression can better shrink the file
|
