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Chapter 4. Creating Web Images > Blurring Images to Aid JPEG Compression

Blurring Images to Aid JPEG Compression

Because of the way JPEG works, the softer the transition from color to color, the more efficiently the image can be compressed. So, if you blur the image slightly, you may be able to reduce the file size—and thus the load time—even further.

Figure 4.61. This is the original image. It has a file size of some 69K.


To blur images to aid JPEG compression:

1.
Create or open the RGB image.

2.
Choose Filter > Blur > Blur (Fig. 4.62). The image is blurred slightly.

Figure 4.62. Choose Filter > Blur > Blur to lessen the differences in the image from one area to another thereby making the compression more efficient.


3.
Save the image as JPEG as described on page 76.

Tip

This is one of those cases in which a little goes a long way. You don't need to blur the image beyond recognition to get file size savings. Don't forget: you want your visitors to be able to recognize what's in the picture.


Tip

You have to decide if the slight loss of detail is worth faster download times and less waiting for your visitors. If all your visitors use 14K modems on 256-bit monitors, this technique may be very useful. Visitors with T1 lines on high-end systems, on the other hand, may not benefit enough from the speed improvement to make sacrificing image sharpness worthwhile.


Tip

Since Photoshop always displays the uncompressed size in the status bar (Figure 4.63), you have to check the size of the image file from the Desktop, or, even better, after it has been uploaded to the server.

Figure 4.63. Your visitors probably won't complain about the loss in sharpness (can you tell?) but they'll appreciate the fact that the image is now only 60K. (The image size given in the status area is the uncompressed size.)



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