Compare images, whichever question you are asking

Which view answers which question

Every view reads the same two pictures, already aligned, so switching costs nothing. Pick by the question, not by habit.

• “Are these the same?” — Smart. A verdict, the share of pixels that changed, structural similarity and a numbered list of changes.
• “Show me both.” — Side by side, with zoom and pan locked together so the same pixel sits under the cursor in both.
• “Show the edit.” — Slider for presenting a change, Fade for spotting geometry that moved a few pixels.
• “What changed, exactly?” — Difference: highlight, mask, heatmap, absolute difference or lighter/darker, with tolerance and anti-aliasing controls.
• “Which one is better?” — Quality measures sharpness, noise, clipping and exposure, and says which picture leads on each without crowning a winner.
• “Did the wording change?” — Text reads both pictures and diffs the words.
• “Are the files different even if the pixels are not?” — Metadata.

Two pictures that are not the same size

Most comparison tools either refuse or stretch. This one first tries to find where Image B sits inside Image A — a scrolled screenshot, a resized export, a 16:9 crop of a 4:3 photo — using phase correlation over a ladder of scales. When the match is confident the transform is applied and disclosed (“B aligned to A: scaled ×0.800, moved 0, 100 px”); when it is not, the workspace says so and falls back to fitting B to A.

You can always overrule it: compare in original pixels over the overlap, fit either picture to the other, place both on a common canvas, or nudge B by hand. None of these touch your files; they change how the two are laid over each other for the comparison.

Change regions instead of a sea of red

A pixel diff of two screenshots is often thousands of scattered red dots. Grouping them is what makes the result usable: neighbouring changed pixels are gathered into regions, small specks below the minimum size are dropped as noise, and each region gets a number, a box, a size and a plain description — “Moved 12 px right at the middle left”, “Colour changed at the top right”. N and P step through them, and each can be marked reviewed or set aside.