transparency â GIF Formatå
Transparent color allows, in fact, create GIF-files of arbitrary shape - pixel image with this color, when viewed in a browser will be invisible. It would seem, since HTML is not (yet) allow superimpose images of each other, or the text, it makes sense to use only on pages that are filled with some background image. However, because of the almost inevitable diffusion in the browser, which we have already said, one has to resort to transparency, even when the page background is painted a solid color, if you fill the background of the figure in the same color, but do not make them transparent, the line between rough background pattern and a smooth background page in the browser is too well marked. Hence it follows that in the picture, use transparency, you can not use the palette reduction with diffusion - because transparency can be declared only one color, and if the background image will be composed of a mixture of different colored pixels, completely transparent to make it will not be possible (though, as we we shall see below, the use of Adobe Photoshop allows you to work around this limitation.)
On the other hand, if the background image that will host your image, fairly uniform in color, you can put a background image in a similar color and make it transparent. In this case, diffuse outer boundary is not terrible, as it will blend in well with the background image. Just do not forget that when the page loads in the browser background image often comes from the network later than the front-end graphics with transparent backgrounds. Therefore, in order not to spoil the impression, tag of your page, in addition to the attribute BACKGROUND, is also useful to point attribute BGCOLOR, picking up the color for him, as close as possible to the main color of the background image.