I am going to show you how to replace your eyes with cat eyes. A relatively simple task, but in working through the details of this simple task, I will cover a handful of indispensable techniques that should be in every photoshop user's tool kit.
So...let's get started!
Step 1: Gather Your Images
First things first. Get a picture of yourself. I used my webcam to grab a quick one.
Next find a good high resolution image of a cat's face. Make sure that the cats head is facing the same direction as yours, so that your eyes will line up properly.
My pictures are both full frontal views.
I grabbed my cat picture from sxc.hu. There are other royalty free image banks out there, like the wikimedia commons for example. But, if you are just doing this for your own personal enjoyment, I don't think there is anything wrong with pulling any old image from any old image search. Or, if you have a cat, even better!
Step 2: Copy Paste
So.... open photoshop. Select File->Open from the top menu bar and open your image and your cat image. You can select multiple images by holding Ctrl or command and clicking.
Find your cat picture go to the top menu option Select-> All.
Then, in the top menu again Edit->Copy.
You can now close your cat picture by clicking File->Close.
Now your image should be visible. From the menu, Edit->Paste.
If your images are like mine, the cat picture will be waaaay too big.
Next we change the size....
Step 3: Resize and Cut It UP!
Click on layer 2 so that it is selecting. (This means that this is the layer that you will be modifying)
So, here is a trick for ya'll!
At the top of the layers pallet you will see the word "Normal". This is your current "blending mode". Click on it and change it to "Multiply". I will spare you the technical explination, but this will allow you to see the layer underneath so that when you resize your image, you can get the eye slightly bigger than your own lovely eyeball!
Now, from the top menu: Edit->Free Transform. Now you will have a box around your cat image.
Click on one of the corners and drag the box to resize the cat image so that the eye is a little bit bigger than your eye. (hold down Shift as you resize so your image does not squish or scrunch!).
You can also click anywhere inside the box to move the layer around.
Press m to select your marquee tool. Use this tool to draw a big box around one of your cat's eyes.
Then Edit-> Copy.
Now you have 3 layers!!!
Click on Layer 2 again.
Select the other eye using the marquee tool and repeat the copy, paste.
Select Layer 2 again and click the little trashcan at the bottom of the layers pallet. (we don't need that rest of the cat face).
Your image should now look like the last in this step's set.
Step 4: Fine Tune the Position
Select one of your eye layers and enter Free Transform mode (Remember that one too, eh???)
Use the corner box to get the cat's eye to the exact size of your eye.
You can also place your cursor to the outside of the box, and it will turn into a curved arrow. Use this to rotate your cat's eye to fit the orientation of your eye.
Select your other eye layer and repeat these steps for the second eye.
Ok..now for the fun part!
Step 5: Layer Masks
Select one of your cat eye layers, then click on the little grey box with the white circle in it at the bottom of your layers pallet. (see image)
This creates a layer mask!!!
A layer mask allows you to make areas of a layer invisible. It is like erasing, but it doesn't actually erase anything (this comes in handy in more advanced techniques - learn it now, use it wisely and often)
So, how does it work????
See that white box that appeared on your selected layer? That is your mask (technically an alpha channel -a visual representation of transparency: black is transparent, white is opaque, 50% grey is 50% transparent etc...)
See that little broken outline around the little white box? That means that you are editing the layer mask, not the image itself. Go ahead, click on the picture of that layer. The broken outline will move to the other image.
Ok, enough playing around...click on the mask again.
Select your brush by pressing b.
select your default brush colors by pressing d.
flip your brush colors so black is in the front by pressing x.
(These are called shortcuts or hotkeys btw)
Press ] a few times until your brush is about the size of your eye, then hold Shift and press [ a bunch of times. Your brush will appear to have gotten smaller, but its edges have just been softened.
Now, use your brush like an eraser removing the fur from around the eye. If you 'erase' to much, just press x to switch to white and paint that part visible again.
OK!! now we are getting somewhere!
Step 6: Adjustment Layers!
ok, so now, Click on your top layer. Then click on the little black and white circle at the bottom of your layers pallet. (see image).
From the little menu that pops up select Curves.
(Now, if you don't know about curves, look into it. If you know what s going on with curves, it is the only image adjustment that you need.)
Ok, but for now. This will create an adjustment layer. An adjustment layer allows you to change things like the brightness and contrast of a layer or stack of layer without actually changing the pixels(dots) that make up the image. This means that you can, at anytime, remove or edit the adjustment layer. Hooray for non-destructive editing!!
Before we do any adjusting, let's set a "clipping mask". This will make the adjustment layer only effect the layer directly below it. Right click on your Curvers layer and select Clipping Mask. A little bent arrow will appear on your adjustment layer.
Ok. now move up to the adjustment panel. (if you are ever missing a panel, check the Window menu at the top).
Place a point on the line in the Curves box and adjust it until the light / dark values of the cat's eye make it start to look like it belongs on your face. (Don't worry about it being perfect, yet) You will most likely want to drag a point at about the middle of the line down to make your darks darker.
Then repeat these steps, making another adjustment layer above the other eye layer.
It should now look something like the last image on this page.
Step 7: Adjusting With a Brush
New Layer time!
Click on your top adjustment layer, and then from the top menu, select Layer -> New -> Layer...
You will now have a layer on the very top of your layer stack. Press b to select you brush again.
We are going to give some color to the eyes. Select a nice bright yellow, green or whatever color you want you eyes to be.
Press 3 to set you brush opacity to 30%, and adjust your brush size to be close to the size of your eye.
In your Layers pallet, once again, select Multiply from the blending mode menu, where it currently says Normal.
Now carefully paint some transparent color over the colored part of the cat's eye. Do not worry about painting over the black part of the eye, because the multiply setting will keep that dark black.
Ok, now select black for you brush color and press 1 to drop your brush opacity to 10%.
Using the very transparent soft black brush, darken the edges of the eyeballs to make the eyes fit the shape of the skull. This will help make it look like the eyes are not just flat, sitting on the face.
Shadows are probably the most important thing when combining photographs. If you can match the shadows (and light for that matter) then you are golden.
Step 8: Final Adjustment!
Make a new Curves adjustment layer by clicking on the black and white circle at the bottom of the layers pallet again.
Make sure that it is at the top of your layer stack, above everything else. If it isn't, grab it and drag it up there.
Now adjust your Curves layer to change the overall tone of the image. I used a slight S curve to subtly darken the darks and brighten the lights in order to create a contrast that is more "moody".
I know that this was a very simple task, but we covered a lot of techniques here, use them wisely and they will serve you well. I hope that you learned some things and are able to apply them to some wonderful and creative projects!
Scratch the surface!