Okay dont ask me what I was thinking when I did this, actually I made this as part of a "live" tutor class at my school, and people kind of liked it, so I'm showing it to you now.
In this Adobe Photoshop tutorial you will see how to manipulate a photo, in this case we will apply a human mouth to an apple, bon appetit.
First we need to prepare our image, so start by importing your apple image on to the stage and with the pen tool select and delete all the surroundings of the apple image.
Then drag the mouth image into the same photo file. You might want to rotate the mouth image just a bit to fit the apple.
With the eraser tool select a soft brush and erase around the mouth to make the mouth "blend" or "soft" in with the apple. It should look something like this.
Now we will separate the teeth from the lips, because we will keep the colors of the teeth white, so with the polygonal lasso tool click around the teeth to select them as shown below. then hold down ctrl and click c (to copy the selection). Again hold down ctrl and hit v (to paste it to another layer above it). In the layers panel click the small eye icon, to hide the teeth part, we will need it later.
Now we will take the lips layer and make it black/white, and try to saturate some different places to make the "shadows" stand out.
So select the lips layer, go to image -> adjustments -> desaturate
Then go to image -> adjustments -> hue and saturations and drag the saturation just a bit to bring out the shadows and highlights.
The before image.
The after image.
Now we will change the blending modes, so locate the blending modes roll down menu, its located just above the layers panel, and set it to Luminosity.
In the layers panel make the teeth part visable again by clicking the small eye icon, now you should have white teeth and pink gums again.
The last thing we need to do is a bit tricky and might take so practice, we need to make the dark areas darker and the light areas a bit lighter, (or maybe even darken some light areas), its more of a personal touch, and you will need to evaluate what looks more realistic.
But the tools we are going to use are Dodge and burn tools, with the dodge tool and a soft brush draw carefully on some areas you want to be a bit lighter and with the burn tool, draw to darken areas. You can see my before and after images below.
The before image.
The after image.
And you are done. You have made your own photo manipulation.