Layering images over one another is a great way to give a photo a new Background, juxtapose unlikely images, or fake a photo-op with your favorite celebrity. Whether you're trying to add a few decorations to a holiday card, or fool someone with a faked photograph, you can use free software to accomplish your goal. Follow these steps to superimpose one picture onto another.
Use this method for simple collages. Follow this method to put together simple pieces of photos into one image, quickly and easily. This method is not for convincing photoshop jobs, but may be what you're looking for to create a fun holiday card or similar amateur creation without taking a lot of time.
For best results, download free photo manipulation software such as GIMP, Paint.NET, or Pixlr. If you happen to own professional software such as Photoshop or Paint Shop Pro, you can of course use them, but purchasing them is not at all necessary.
Because this method requires only a few tools, you can use this method with simple software not mentioned above, such as Windows Paint. However, you may not have access to a "feather tool" to create a more attractive result, and without "layer" functionality, it will be easier to mess up and cover portions of your photos you meant to keep.
Open the background image first. This is the image that will serve as a background for the image or images you will superimpose. Use your photo editing software to File → Open it.
Use File → Save As to save it under a new name if you want to keep the original version. You can also do this after you're done, but if you do it in advance there's no risk of forgetting and overwriting your file.
Open the image you want to superimpose. You will transfer part of this image on top of the background image. Use the same program to open the second image in a new pane. For this one, you'll definitely want to File → Save As now under a new name to avoid altering the original.
Select the circular selection tool. You should see a grid of buttons with different images on it, usually to the left of the screen. These are your tools. Click the circle or oval made of dashed or dotted lines, usually located near the top of the list.
You can hover you mouse cursor over a tool and wait for the name to appear to confirm your selection. It may be called "ellipse selection", "ellipse select", or a similar name.
If you can't find that selection tool, you can use the rope "lasso tool" or the square "rectangle select" tool instead.
Click and drag around the portion of the image you wish to transfer. Drag around the person, animal, or other piece of the image you want to overlay onto a different background. Try to find a selection that looks attractive, with the subject centered and no incongruities included (like someone else's arm coming in from the side).
Most photo manipulation programs come with a Invert Selection command, which selects everything except what you currently selected. This is handy for seeing what your selection looks like by itself: use Ctrl + Shift + I (or command + Shift + I on a Mac) to invert selection, then Edit → Cutto remove everything but the image you'll be transferring. Be ready to Edit → Undo so you can try different selections.
If you dislike every selection, you may need to follow the steps for Overlaying a Detailed Image.
Soften the edges of the selection (optional). The resulting image may have harsh or strange-looking edges, which can make the final result seem unnatural or obviously manipulated. You can adjust this by using a "feather tool" or "feather setting" to soften the edge, but be aware that different programs require you to access the feather ability in different ways:
In Photoshop, right click the selection and click Feather.
In Gimp, use the top menu: Select → Feather.
In Paint.NET, you will need to download the Feather Plugin and open that plugin's menu to use this tool.
In Pixlr or Paint Shop Pro, click the selection tool and alter its feather setting before making a selection.
In any program, you should see an option to enter a numeric amount determining how extreme the feathering effect will be, measured in pixels. Start with 1 or 2 pixels for this method to avoid losing fine details.
Once you find a selection you're happy with, copy and paste it onto the background image. You can do this with the Edit → Copy and Edit → Paste commands, making sure to select the desired background image you opened earlier before pasting.
If everything but the selection gets copied, you need to use the Invert Selectioncommand a second time to get back to the original selection.
Re-position and re-size it to scale. Select the move tool, which looks like a cursor arrow or a four-point compass, then click and drag the superimposed image to the desired location. If you need to change the size of the overlaid image, follow these steps:
Go to File → Free Transform (or hit Ctrl + T) to transform the image.
A box should appear around the superimposed image; click and drag the sides and corners to change the size and shape. To maintain the proportions, hold Shiftwhile clicking and dragging a corner.
If the wrong thing moves, make sure you’re on the right layer by going to View→ Layer or Window → Layer, then clicking the layer that contains the superimposed image.
Use File → Save As to save the result under a new name. Make sure that you've selected the image that contains the final result before saving. It should be in front of any other images.
You can add additional pictures to this picture in the same way, no matter how many times it's been altered.
In order to change which pictures are placed over or under other photos, reveal the Layers menu with View → Layers or Window → Layers on the top menu, then drag each photo thumbnail higher or lower on the list. The lowest layer should always be the background image, while the highest layer will always show up in full on top of everything.