Selectively compress areas of a JPEG

To reduce the overall size of the image while retaining the quality of the more important areas, compress areas of particular interest at a higher quality level, and compress areas of lesser significance, such as backgrounds, at a lower quality level.

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.

1. In Original view, select an area of the graphic for compression using one of the Marquee tools.

2. Select Modify > Selective JPEG > Save Selection as JPEG Mask.

3. Select JPEG from the Export File Format pop-up menu in the Optimize panel.

4. Click the Edit Selective Quality Options button in the Optimize panel.

5. Select Enable Selective Quality and enter a value in the text box.

   Entering a low value compresses the selected area more than the rest of the image; entering a high value compresses it less than the rest of the image.

6. (Optional) Change the Overlay Color for the Selective JPEG area. This does not affect the output.

7. To export all text items at a higher level regardless of the Selective Quality value, select Preserve Text Quality.

8. To export button symbols at a higher level, select Preserve Button Quality.