Panorama Photo Stitcher

A panorama photo stitcher takes several overlapping photos and turns them into one image. The idea is simple. Doing it well involves finding common details, working out how the camera was turned between shots, projecting everything onto a common surface and blending the overlaps so the joins disappear. This page explains each step in plain language and describes how Panorama 360 stitches on your phone.

Panorama 360 is coming soon to Android and is not on Google Play yet.

What stitching means

Image stitching is the process of combining images with overlapping fields of view into a single larger image. It is used for landscape panoramas, 360° photos, aerial maps and even microscope images. The general idea is covered on the Wikipedia article on image stitching, and the research that shaped modern panorama software is summarised in the paper Automatic Panoramic Image Stitching using Invariant Features by Brown and Lowe.

Step 1: Overlap and feature matching

Software looks for distinctive details, such as corners, edges and texture patterns, in each photo. It then finds the same details in neighbouring photos. These matches show how one photo relates to another. Without overlap there is nothing to match, which is why the app guides you to overlap each photo by roughly 30 percent.

Step 2: Alignment

From the matches, the stitcher estimates how the camera turned between photos. Panorama 360 gets a head start: your phone's motion sensors record which way the camera was pointing for every photo, so the stitcher begins with a good estimate and only needs to refine it. It then adjusts all photos together so that the matched details agree as well as possible across the whole panorama. If a scene has too little detail to match, for example a blank wall, the result relies more on the sensors, and the app reports that.

Step 3: Projection

A panorama has to be drawn on something flat. Common choices are cylindrical and spherical projections. A full spherical panorama is stored in equirectangular form, a 2:1 image where horizontal position is longitude and vertical position is latitude. See our page on spherical 360° panoramas for how that format works.

Step 4: Exposure and blending

Photos taken moments apart often differ in brightness. The stitcher estimates a gain for each photo so overlapping areas match, then blends each overlap with a smooth transition, rather than a hard edge, to hide the seam. Blending can hide small differences. It cannot hide big alignment errors.

Why artefacts appear

• Parallax. Close objects shift relative to the background when the camera moves sideways. See Wikipedia on parallax. Turning on the spot avoids most of it.
• Moving subjects. People or vehicles that moved between photos can appear twice or be cut in half.
• Exposure jumps. Large brightness differences can leave visible steps.
• Low-texture areas. Clear sky, white walls and still water give the matcher little to hold on to.
• Blur. Blurry photos have fewer reliable details.

The article how photo stitching works goes deeper on each of these.

Panorama 360's stitching workflow

1. You capture photos inside the app. The app records the phone's orientation for each.
2. When you finish, stitching runs on the phone and shows progress. You can cancel and retry.
3. The app checks the result. A complete sphere is labelled a full sphere; a turn around the horizon is labelled a horizontal 360° panorama; anything with gaps is labelled partial.
4. You can look around the result, make light edits and save or share it.

If stitching fails, for example because photos were unreadable or there were too few, the app says so and keeps your photos instead of returning something misleading.

Input and export

Input is photos captured with the app, in either capture mode. Export is a JPEG with Google's spherical panorama metadata, so compatible viewers show it as a 360° image. Free exports are limited to 4096 pixels wide and carry a small Panorama 360 mark. Paid plans export at full resolution without the mark. The app does not stitch arbitrary photos you import from elsewhere.

Reducing problems before you stitch

Most stitching problems are capture problems. Rotate around the phone, hold still, keep distance from close objects and wait for people to pass. Our 12 panoramic photography tips cover this in more detail, and the 360° panorama camera app page shows how the guidance works in the app.