I came across this nifty little feature in Fireworks that will help you compress a JPEG even further. Selective Quality JPEG allows you to compress different parts of an image at different compression levels.
In the examples below the first image is set to a JPEG quality level of 85 for the whole image, which makes the file 85KB. The second image has the area of the person on the bike compressed at 85 and the background and foreground set at 65, which brings the file size down to 55KB, saving 30KB and retaining the quality of the focal point of the image.
Image 1
File Size: 85KB
Compression level: 85
Image 2
File Size: 55KB
Compression level: 85 on focal point, 65 on background and foreground
So this is how you do it in Fireworks:
Step 1:
Open the image you want to compress
Step 2:
Choose the lasso tool from the tool bar and select the area you would like to compress at a different level.
Step 3:
Go to MODIFY > SELECTIVE JPEG > SAVE SELECTION AS JPEG MASK
You will now see your selection area turn a shade of red.
Step 4:
Go to the Optimize Panel and click the ‘Selective Quality’ button to set the JPEG compression level of the selected area. and set the ‘Quality’ level to set the compression level for the rest of the image.
That’s it, you just export and you’re done.