Adobe 38039927 - Fireworks CS3 - PC Using Instructions page 278

Adjusting JPEG quality
JPEG is a lossy format, which means that some image data is discarded when it is compressed, reducing the quality
of the final file. However, image data can sometimes be discarded with little or no noticeable difference in quality.
Original image; quality setting of 50; quality setting of 20
To control how much quality is lost when compressing a JPEG file:
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Adjust the quality with the Quality slider pop-up menu in the Optimize panel.
A high percentage setting maintains image quality but compresses less, producing larger files.
A low percentage setting yields a small file but produces a lower-quality image.
Selectively compressing areas of a JPEG
Selective JPEG compression lets you compress different areas of a JPEG at different levels. Areas of particular interest
in an image can be compressed at a higher quality level. Areas of lesser significance, such as backgrounds, can be
compressed at a lower quality level, reducing the overall size of the image while retaining the quality of the more
important areas.
The selected area in this image is being compressed at a quality level of 90, while the unselected area is being compressed at a quality level of 50.
To compress selected areas of a JPEG:
1 In Original view, select an area of the graphic for compression using one of the Marquee tools.
Select Modify > Selective JPEG > Save Selection as JPEG Mask.
2
Select JPEG from the Export File Format pop-up menu in the Optimize panel, if it's not already selected.
3
4 Click the Edit Selective Quality Options button in the Optimize panel.
The Selective JPEG Settings dialog box opens.
Select Enable Selective Quality and enter a value in the text box.
5
Entering a low value compresses the Selective JPEG area more than the rest of the image. Entering a high value
compresses the Selective JPEG area less than the rest of the image.
Change the Overlay Color for the Selective JPEG area if desired. This does not affect the output.
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ADOBE FIREWORKS CS3 273
User Guide