Using Adobe Photoshop Elements 5.0
Uses Color Fills, Levels, Brightness/Contrast, Gradient Maps
Level of Difficulty: A beginner can probably follow along and learn
As aforementioned, I did not intend to work with icons today, much less write a tutorial for one. However, as I was toying around in Elements, I discovered a method I liked as I was trying to clean up this Harry Potter and the Prisoner of Azkaban screencap. The main focus on this will be the eventual use of Gradient Maps. It's a good tool to try and get ahold of when fixing the coloring of an icon.
This was intended for duller, lighter screencaps that needed preparing. Bear this in mind when you read the tutorial. Obviously this cap is from a stormy pic, rain and dark clouds. I kept remembering this as I worked with the steps; I did not need a bright blue sky so I did not strive for one. Look at your picture. What does it need to look like at the end? As I go through the steps, work with them until you find what you need to make your picture look better.
1 - Choose your screencapture and reshize it down to fit a blank icon. Think about composition, how your subject should be aligned.
Duplicate your base. It will be the safe canvas to work with as we prepare our layers. Do not be fooled into thinking that just because the image is bright that you will not need a Screened layer. For a lot of general icons, you do. Go ahead and make one, but keep the opacity down. Mine did not need much. Now start bringing out the tones with a solid Overlay, Soft Light, or Hard Light. Fool around with those three, because skin tones are at the mercy of which one you need to use. Mine worked well with Overlay. And since I wanted an even stronger tone, I went ahead and duplicated that layer, bet set it at a lower opacity.
2 - There's that deep blue sky I wanted nothing to do with. I needed to set the storm back in, but at the same time improve the colors of the Seeker. A Color Fill will work fine here, so that's not much to worry about (Layer->New Fill Layer->Solid Color). Keeping Overlay at a bit above mid opacity, I looked around at the colors. Red was too strong, and did not mix with the background. Blue made it too dark. The yellows looked good, but to preserve the darks I chose to take it down into the browns.
Suddenly I see colors. Overlayed Color Fills are a magnificent tool that you Element (and PSP) users can use when you find that a color is not as well toned as you would like. You need not worry about Saturation and all of that, when this process is somewhat easier. That's my opinion. You learn to use either what you find easier or what technique you enjoy using more.
3 - It's time to secure highlights and shadows through a Levels layer (Layer->New Adjustment Layer->Levels), set to Normal (anything else at this point might make it too dark or too light).
I am usually one to shy away from the output layers, but toying around with them made me realize that they help right alongside the input layers when it comes to improving (or if you're not careful, breaking) the picture. I'll try and break it down a bit better. First focus: RGB
This is your master option, the main control of your lights and darks at this point. For this, I stay with input. There's no better way for me to tell you how to use this function other than just practice moving those three arrows (black for shadows, gray for tones, white for highlights) over towards each other until yours is set on something that makes you content. Mine did not need too much movement from either three of them. I inched over the black and whites arrows from either side a little, but for the most part left them alone. My focus at this point was on the colors.
Reds: With this particular picture, my Reds controlled my reds (imagine that) and (in this case) teals. The white arrow will control the Levels' dominant color, which for this is red. Moving it to the left will cause those warm colors to highlight in the input section, but if you move the white arrow in the output section, it shadows them with the opposite color. I needed some focus on my golds and pale blues at the same time, which can be difficult. Reds helped take care of transforming yellow to gold, and the output section (much to even my surprise) helped keep it under control so as to work with the blue background.
I applied the same mode of thinking for the Greens and Blues. I could tell you exactly what I set them to, but it won't help for your picture. This step is your responsibility to learn and to use.
4 - Now I wanted some contrast and I also wanted to start working on the darks. Enter Brightness/Contrast (Layer->New Adjustment Layer->Brightness/Contrast) set on Soft Light.
Pending how busy your icon is, Contrast will help separate the objects (like the Seeker) from the background and other objects. Brightness is self-explainatory, but take care with both of them. Chances are, you will not need to set either very high, especially if you set this as a Soft Lighted layer.
At this point the colors are still not where I really want them to be. Keeping the layer as a Soft Light or Overlay, if you are in this position, try another Color Fill. I stuck to the yellows/golds/browns as I previously did to both tone up Hufflepuff's colors and tone down the sky.
If you do not have the following tool, do not worry. I tried to make it so that you could stop, if you needed to, right here. This next step is for Photoshoppers, to make a better difference.
5 - Now comes for the Gradient Maps (Layer->New Adjustment Layer->Gradient Map), set to Soft Light. Depending on which filter you choose matters on how high the opacity is going to be. I kept mine low.
Let's not beat around the bush. If you're new to Photoshop, this thing is a beast. But, it's a tool that can really help you out for coloring your icon when used in a respectful manner. When you click on the arrows, you'll be given a list of choices to give you many, many options on what to use on your icon. Within those many choices, you have the option of reverse, giving you twice as many filters as before. Toy around with this. It's a fun tool. If you want to keep around the realistic coloring, consider Spectrums as a good option. I chose the Medium Spectrum because of it's flat, smooth effect on normal tones. It's also not too overpowering. The spectrums are good for beginners trying out Gradient Map.
Because I wanted even more depth, I made another Gradient Map layer. This time I looked around the Color Harmonies until I found the gradient team that complimented the existing color scheme of my icon the most. Set to Soft Light, this was the final result.