If there are no needs for superior quality, you go with a fixed numerically generated palette (commonly 6 shades of each red, green and blue, the "web-safe palette" or 8 shades of both red and green combined with 4 shades of blue), and you apply no dithering or very simple regular dithering algorithms (like "round up the odd pixels, round down the even pixels"). The latter one makes finding the appropriate color index from the high-color RGB values and dithering correctly more easy. The former choice allows way better pictures, but requires slow algorithms for color mapping (in case of 16bpp->8bpp, you can cache that mapping in a lookup table), often resorting to brute force searching. The primary concept for appealing dithering result is error diffusion, and the Floyd-Steinberg algorithm is a common realization of that idea.Įven in case you need to choose a general purpose fixed palette, you can optimize the palette for having their colors chosen for approximately equal visual difference (more shades of green than shades of blue, more bright colors than dark colors), or for equal spacing of the RGB values. There are more advanced dithering methods that create more pleasing results, but they are noticeably slower. There are two fast ways for down-converting high color images: Just choose the nearest palette color (creates awful banding) and dithering with a regular pattern derived from the low bit(s) of the X/Y coordinate values (generates annoying patterns). In case you want to display multiple arbitrary images at a time, you can not optimize the palette to specific images, but you would need to settle on a common palette for all images. Properly choosing the palette color immensely reduces the amount of color errors you had to conceal. If you want to display only a single image at a time, you can create a palette adapted to that image.
There are two key points to generating good looking 256-color images: Choosing a proper palette and obscuring color errors (usually by some kind of dithering).
They have to have been taken at a higher bit depth and downleveled to 8 bit what happened? Why are the converters immediately at our fingertips so bad and how could they be good? The images could not have been taken with an 8 bit camera. The images are reasonable much better than someone dealing with 16 bit to 8 bit conversion would expect.
8BIT COLOR PALETTE CONVERTER PC
This is not rose colored glasses-my multimedia PC era CDs are still readable and I called one up to verify. But neither the videos nor the images are the terrible of reducing 16 bit depth to 8 bit depth. Granted, they show so many artifacts now that the videos look bad to modern eyes. I used to painstakingly hand-construct 256 color images.īut we had these encyclopedia and other programs that had 256 color images and videos that were awesome at the time. You had to be a really good programmer to make it come out well because of palette control (and the background program always went to trash) but it worked. It was the same in the late 90s when I had access to 16 bit depth converting to 8 bit depth was terrible.īut I remember the days of the Multimedia PC and S3 cards and 8 bit depth. If I take a 24 bit image and reduce it to 8 bits with save as of any simple drawing, the result is terrible as any modern computer user would know.
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