User Guide

GNU Image Manipulation Program
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Delay between frames if unspecified Delay between frames if unspecified : you can set the delay, in millisecondes,
between frames if it has not been set before. In this case, you can modify every delay in the Layer Dialog.
Frame disposal when unspecified Frame disposal when unspecified : If this has not been set before, you can set how
frames will be superimposed. You can select among three options :
• I don’t care : you can use this option if all your layers are opaque. Layers will overwrite what is beneath.
• Cumulative Layers (combine) : previous frames will not be deleted when a new one is displayed.
• One frame per layer (replace) : previous frames will be deleted before displaying a new frame.
6.1.2.2 Saving as JPEG
JPEG files usually have an extension .jpg, .JPG, or .jpeg. It is a very widely used format, because it compresses images very
efficiently, while minimizing the loss of image quality. No other format comes close to achieving the same level of compression.
It does not, however, support transparency or multiple layers. For this reason, saving images as JPEG often requires them to be
exported from GIMP.
Figure 6.3: The JPEG Save dialog
The JPEG algorithm is quite complex, and involves a bewildering number of options, whose meaning is beyond the scope of this
documentation. Unless you are a JPEG expert, the Quality parameter is probably the only one you will need to adjust.
Caution
After you save an image as a JPEG file, the image is no longer considered ‘dirty’ by GIMP, so unless you make further
changes to it, you will not receive any warning if you close it. Because JPEG is lossy and does not support transparency
or multiple layers, some of the information in the image might then be lost. If you want to save all of the information in
an image, use GIMP’s native XCF format.
Quality When you save a file in JPEG format, a dialog is displayed that allows you to set the Quality level, which ranges from 0
to 100. Values above 95 are generally not useful, though. The default quality of 85 usually produces excellent results, but