How to Diagnose Image Transparency Problems
When a supposedly transparent image shows a box, start by inspecting its actual alpha channel.
Method
JPEG cannot preserve alpha; converting transparent PNG to JPG flattens the background to a matte color. Semi-transparent edge pixels can create a halo against a different destination background. Inspect alpha counts and bounding boxes, then trim empty space if necessary.
Verification and limitations
A checkerboard preview is not evidence that pixels are transparent; read the actual alpha channel and compare on light and dark backgrounds.
Related working tools
Further reading: https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/getImageData (reviewed October 16, 2026; externally maintained, specifications may change).
Last reviewed: October 16, 2026. This guide is general education; test your intended upload or publishing workflow independently.