JPEG Collager is a JPEG (and BMP) viewer which shows each image in a window without any Border. The best way to see how it works is to play with it a bit, but here is a summary of use.
You can open any number of images. Images can also be opened by dropping the file on the tool window. Each one is manipulated individually. On the tool window in the title bar you can see which image the mouse is currently over. The Active Window (the one which will be affected by operations) is indicated on the left of the status bar; the right of the status bar shows the dimensions of the image and the window. When you see the icon become a hand, left dragging moves the window and right dragging moves the image within the window (unless it is stretched to fill the window). The window can be sized by dragging the edges.
The Stretch option causes the image to fit the window. By default, Maintain Aspect Ratio is on. This means that the picture will not be distorted but resized to the height or width you select. For it to take effect (visually), you do have to resize the window. If you turn off Maintain Aspect Ratio, the image will be distorted to fit whatever window size you choose. The Stretch tool button will appear depressed to show that Stretch is active. The status bar will also say "Stretched to" the window dimensions.
If stretch is off, clicking Fit Image resizes the window to show the whole image.
To create collages, you may want to first create a new window, set the color to your preference, and maximize it. The simplest way to Capture the collage is to click the camera button on the toolbar; this will take a screenshot of your primary monitor. Create a new window and paste it in with the menu, toolbar, pressing Ctrl-V.
New in version 1.2:
Now says "Empty file!" instead of "JPEG Error #41".
Nicer toolbar.
Corrected screenshot action.
Can now open by drag-n-drop.
Remembers open and save directories.
Remembers position on screen.
Remembers background color.