Bitmap Export Dialog Box - Preview boxes
These let you preview the appearance of the graphic before you export it. This is particularly important for web graphics where selecting suitable parameters reduces the file size without significantly reducing image quality. You can also swap between different bitmap formats (GIF, PNG, BMP, & JPEG) to check which works best. The Preview Boxes make this checking quick and easy. For more details see Previewing bitmaps.
More information on the Zoom, Push and Color Picker buttons.
In the various tabs set the options you want to try. This automatically updates the preview.
If these options are worse than the previous settings, you can try again and overwrite the last preview image.
If the options are better and you want to try to get further settings, click on the other Preview Box to overwrite that image. This preserves the current best settings.
When you are satisfied with the results, select the best preview and click Export.
You can also preview the graphic in your browser using the Browser Preview tab. This is useful as a final check or when testing image maps.