![]() ![]() This is the same RGBA image on top of a checkerboard background. In this case, the background is a light blue color. The portions of the alpha channel are blended with the background. This picture combines the RGB image with the alpha channel, forming an RGBA picture. By itself, it identifies the relative intensities of the pixels. This picture has no alpha channel and is completely opaque. The following sample images demonstrate the use of a gradient alpha channel. GIF only supports a boolean alpha channel. ![]() (A pixel is either transparent or it isn't.) While this does not permit smooth blending along borders, it does permit transparency. Boolean alpha channels only use 0% and 100% opacity values.Gradient alpha channels are supported by PNG files, as well as WebP, ICO, ICN, and other bitmap file formats. If the web page's background changes color, then the image does not need to be recreated in order to blend onto the page. For example, the FotoForensics banner at the top of this page uses a transparent background to blend the logo seamlessly with the web page. Gradient alpha values are typically used to blend an overlay picture onto another image or into a web page.Intermediate values determine how much of the background should be blended with the pixel's RGB value. An alpha channel value of 100% (white) means that the RGB value is completely opaque (non-transparent). With the scaled value, 0% (black) denotes a location in the image where there should be complete transparency - the RGB value is ignored and the background is completely visible. With most image formats, the alpha channel is either boolean or a value from 0% to 100% (or 0 to 255 in byte values). The resulting RGBA image defines the visible colors and the degree of transparency. A fourth channel, called alpha (denoted by the letter "A") can be combined to define a transparency level. Pictures are not limited to three color channels. These three color planes are called channels the red color channel stores all of the red intensities, the green channel stores green intensities, and blue stores blue intensities. ![]() When pictures are rendered on the computer screen, colors are created by combining red, green, and blue components. ![]()
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