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Realtime Image Compression
Image compression is one of the most important Web production tasks that designers perform. Adobe
ImageReady provides innovative support for this task with its LiveView window. This window lets you look
at the original image and the final compressed image at any time in the production process, and preview
how the compression settings affect the display quality. For example, you could display an original 24-bit
RGB image and a JPEG-compressed version of it, and then switch between these views to see how different
compression options affect the on-screen display. This process would normally involve saving and then
reopening the file to see any JPEG artifacts.
The Optimize palette offers a comprehensive set of compression options. You have a choice of four standard
Web file formats: GIF, JPEG, PNG-8, or PNG-24. You also gain fine control over the options associated with
these file formats. For example, with GIF and PNG-8 files, you can specify the type of colour palette used, the
number of colours saved with the image, the transparency of the image, and more. The following sections
discuss these options in more detail.
Touring the LiveView Window
In addition to helping you make aesthetic tradeoffs, the LiveView window presents practical information
about current and compressed file sizes, and estimated download times at different modem speeds. You can
also change your zoom view of the image from 12.5% to 400%.
An overview of the LiveView window
F
E
Try it:
1.
Choose File > Open > Hammer.psd.
2.
Note that GIF is selected in the Optimize palette (if necessary, choose Window > Show Optimize).
3.
Click the Optimized tab in the LiveView window to preview what the compressed graphic looks like
(a progress bar appears as ImageReady generates the compressed version). Alternatively, use the key-
board shortcut Ctrl+Y/Command+Y to switch views (you may not see a lot of difference on-screen yet
because the current settings suit the image well).
4.
Switch back to the Original view of the image. Note that the original and optimised file sizes
appear at the bottom of the palette.
5.
Choose Size/Download Time (28.8Kbps) from the pop-up menu to view the estimated size of
the optimised image and approximate amount of time it will take to download.
6.
In the Optimize palette, click the Colours pop-up menu and change the setting from 32 to 16.
7.
Switch to the Optimized image view to see how this new setting affects the image. Note how
grainy the colours now appear. That's because we've reduced the colours too far. Also note that this
choice reduced the estimated final file size by several K.
A
B
A
Click the Original and Optimised tabs to toggle between views
of the original and compressed image.
B
Compare the original and compressed images in this LiveView
window.
C
Drag to resize the window and display all the pop-up menus.
D Display different information options, such as file size and
estimated download time at a particular modem speed.
E
Display and view the image dimensions.
F
Zoom in or out of the image by choosing zoom levels from the
pop-up menu.
D
C
4
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