Can someone explain in simple terms how removing the background from an image works? I noticed the BBC logo during the Euro final is semi-transparent, and I’m curious about how that transparency is achieved.
How does an image display transparency, and what are the limitations? Also, what happens when a transparent image is placed on top of another image or another similar image—what happens to the “transparency”?
In: Technology
your monitor has red, green, and blue subpixels that it can set to any value between off and full on, this lets them make pixels of any color.
Since all monitors work this way, images are stored in pixels using 3 numbers per pixel one for red, one for green, and one for blue. This is called RGB encoding. to add transparency, you add a 4th number to each pixel referred to as Alpha to make ARGB. This number says “this pixel is this percent visible”.
When layered, the computer says “ok, this RGB pixel is under this ARGB pixel, so take the ARGB, scale its RGB values by Alpha and combine it with the pixel’s existing RGB value” There are various ways to combine them, but the one that “looks right” is alpha blending where the final color is [Base] x (100% – alpha) + [new] x alpha
for multiple argb images, just combine them 1 at a time, bottom up using the output from each combination as the base for the next
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