Saving 4-Bit images in Adobe Photoshop
If you are a designer working with a development team who is building a piece of stand-alone software, chances are you’ve experienced the need to provide them with 4-bit graphics and icons. It’s not something that is entirely intuitive to do in Adobe Photoshop, but there is a simple solution.
But first, what exactly is a 4-bit image? It could be explained with complex chart and graphs, but the easy answer is this: there basically 15 colors in a 4-bit image. If your image uses only 15 colors, then you won’t have a problem saving as 4-bit. But what if you want to take an existing image with lots of colors and save a 4-bit version of it?Try saving an image (any image) as a bitmap in Photoshop. You will notice that only several of the higher bit-depth options in the “Save” dialog are available and the rest are grayed out:
Photoshop Save Bitmap Dialog
Why does it do that? Well, the options available to you are based directly on the number of colors in the image you are trying to save. As you can see in this example, the options for 8-bit, 4-bit, and 1-bit are disabled. This is because the image I was trying to save contained too many colors to be saved with lower bit-depths.
Theoretically, you could create a 4-bit image in Photoshop by just using the “save for web” option and manually select the 15 colors you want to use. But really – who has the time for that level of anal selection? I sure don’t – so here’s a much simpler way to do it:With your image open, go to “Image > Mode “ and select “Indexed Color”
Photoshop Image Mode Menu
A popup dialog will appear:
Photoshop Indexed Color Dialog
Leave everything in the default settings – chances are that your image will look the best with this standard configuration, but feel free to tinker with some options just to see if you can get it any cleaner. The nice thing about Photoshop is that your image will change as you make your selections, so you can preview what it’s going to look like before you hit “ok”.
Hit the “OK” button, then save your image as a gif (“file > Save As…”). Close the image. Finally, re-open that gif file you just created, and save it as a bitmap (“file > Save As…”). Voila! The 4-bit option is now available.
Note that you can bypass the whole “Image > Mode” step by just saving your original image as a gif from the “file > Save As…” menu. The only downside to doing this is that you will be missing out on all the options available to you by manually changing the image mode yourself.