To prep cutout pieces for animation in Flash, you should crop the files to have a minimal region of extra pixels around them, and make sure the backgrounds/perimeters are transparent. You should use PNG files.
To Crop an Image
Use the Selection Tool to closely select an image. Once you drag a bounding box around it, you can fine-tune the selection by using the context-menu and selecting Transform Selection. You can use the handles on that particular bounding box to get even tighter. When it’s just right, hit the Enter Key to commit to the selection.
To make a copy of the selection, go to Main Menu > Edit > Copy, then to the Main Menu > File > New. Photoshop will recognize that you have a copied material in the clipboard (i.e., Preset > Clipboard). Press OK. The new file will be the same dimensions as the region you copied. Choose Edit > Paste, and Photoshop will add the material to the new file.
To Save an Image in the PNG format
Referring to the Main Menu, go to File > Save for Web & Devices. From the the Save for Web window, refer to the right-hand side of the program’s layout and check the “Preset” options. Using the pull-down menu, choose “PNG-24.” If the image has transparent regions, make sure that “Transparency” is selected, and deselect “Interlaced.”
Then, press Save and give the file a short name.
To carefully evaluate the quality of the image and what it might look like by compressing it, use the “2-Up” tab in the main window, to assess the original image, side by side with the web optimizations that you do.
From the Save for Web Window, you can resize the image.
Referring to the pull-down menu at the top right-hand corner of the Save for Web Window:
- Select “PNG-24″
- Select “Transparency” if the image has transparent regions (it probably does)
- Deselect “Interlaced”
Finally, choose Save. Photoshop will direct you to decide where to save the file. When you name the file, make sure the “.png” is the extension on the file name.