A before-and-after comparison is easier to read when both photographs sit in one file with a shared edge. You can join two images on a canvas, align their heights, and export a single picture. To put the photos together cleanly, preserve each image’s proportions and decide whether to crop or leave space around it.
The example below uses the free desktop editor GIMP and two landscape photographs. To combine images in another editor, use layers and inspect the final size.
Combine Photos: Plan the Canvas
Start by checking each photo’s pixel dimensions. The canvas must fit both pictures, their gap, and any margins.
For a concrete example, suppose both source photos are 1,200 × 800 pixels. Place them at their original size with a 40-pixel gap and 40-pixel margins on all sides. The canvas needs to be 2,520 pixels wide: 40 + 1,200 + 40 + 1,200 + 40. Its height is 880 pixels: 40 + 800 + 40. This leaves a clean frame without changing either photograph.
If the originals have different dimensions, choose a common height and calculate each new width proportionally. A 1,500 × 1,000 photo scaled to 800 pixels high becomes 1,200 pixels wide. A 1,000 × 1,000 photo scaled to the same height becomes 800 pixels wide. With the same gap and margins, the canvas would be 2,120 × 880 pixels. Equal heights do not require equal widths.
Create the layout in GIMP
Open GIMP and choose File > New. Enter the example canvas dimensions in pixels. Choose a white background if you want a visible border, then create the image. Use File > Open as Layers to add both photographs; each appears as a separate layer above the background. The GIMP manual documents these layer and export commands.
Select the first photo layer in the Layers panel. If it needs resizing, choose Layer > Scale Layer. Keep the width and height linked, enter the target height, and apply the change. Repeat for the second photo. The linked dimensions preserve the aspect ratio, so faces and objects retain their shape. Scale a layer rather than the whole image when only one photo needs adjustment.
Use the Move tool with the desired layer selected to place the first photo at the upper-left position inside the margin. Place the second beside it. For the 2,520 × 880 example, the top-left corners should be at approximately x=40, y=40 and x=1,280, y=40. Zoom in to inspect the gap and outer edges. Guides can help you align the top edges; use the ruler or guide commands in your version of GIMP.
Save an editable project as an XCF file before exporting. Keeping separate layers lets you reposition either photo later without rebuilding the layout. To combine two images into one finished file, export the visible composition after checking the placement.
Preserve proportions when sizes differ
A photo’s aspect ratio is its width divided by its height. If you change the width and height independently, a circle can become an oval and a face can look stretched. Keep the link or lock icon enabled when resizing, then enter one dimension and let the editor calculate the other.
There are two common ways to fit mismatched shapes. Fit keeps the entire photo visible and may leave blank space in a fixed-size slot. Fill covers the slot but requires cropping some of the image. For example, a square image can sit whole inside a wide rectangular space with margins, or it can fill that space by losing some of its top and bottom. Choose based on whether the edges contain important content.
Avoid enlarging a small source much beyond its original pixel dimensions when detail matters. The editor can estimate extra pixels, but it cannot recover detail absent from the source. If the final image looks soft, use a smaller canvas or find a higher-resolution original. When you merge two images, start with copies of the source files so the originals remain available.
Align for a useful comparison
For a before-and-after pair, match the scale and position of the shared subject. If a building appears larger in one frame, viewers may mistake a crop change for a change in the building. Align a stable feature, such as a window or horizon, and crop both sides consistently when possible. Keep any labels outside important visual details.
When you combine photos of people, a side-by-side portrait pair may need a different treatment. Align eyes or shoulders rather than blindly matching the top of each frame. If the original compositions differ too much, use a neutral margin around each instead of cutting off a head or hand. Combining photos works best when the arrangement supports the comparison you want the viewer to make.
Check the junction at normal viewing size. A gap separates two independent scenes; no gap can create a more continuous panorama-like effect. Make sure a no-gap join is intentional, because mismatched horizons or lighting can make the seam distracting. This side-by-side layout does not automatically blend or stitch overlapping scenes.
Choose an online tool or a layer editor
An online photo combiner can be convenient when you need a quick pair and do not need precise positioning. Look for controls for layout, spacing, output size, and download format. Check whether it uploads your images to a server and review its privacy terms before using private photographs.
A pic combiner with fixed templates may crop images automatically. Preview the full frame and look for a fit option or adjustable crop before exporting. A layer-based editor provides precise control and an editable project.
If you combine image A with image B in a template, check whether each photo can be moved independently. Save a copy of the result under a new name, especially when the tool offers to replace an existing file.
Export and check the result
In GIMP, choose File > Export As and select a new filename ending in .jpg or .png. JPEG is practical for photographs and smaller files; choose a quality setting that keeps visible detail without making the file unnecessarily large. PNG supports transparency if your layout needs it, though photographic files can be larger. Export a separate copy rather than overwriting an original.
Open the exported picture in a viewer. Check that you have two images in one file, the dimensions match the intended destination, the gap is even, and neither subject is distorted. Zoom to actual size to inspect sharpness and any JPEG artifacts. If something looks wrong, return to the XCF project, adjust the layers, and export again.
Now choose two photos, note their pixel dimensions, and calculate the canvas width and height. Create the canvas and place the first layer; the numbers will make positioning the second much easier.
