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Bit Depth是一个术语，用来描述图片中用来表达颜色需要用到的bit数。
声音数据也有bit depth概念。
每一个像素（pixel）都需要表示颜色的bit，这些bit越多，能够表示的颜色也就越丰富。
Every color pixel in a digital image is created through some combination of the three primary colors: red, green, and blue. Each primary color is often referred to as a "color channel" and can have any range of intensity values specified by its bit depth. The bit depth for each primary color is termed the "bits per channel." The "bits per pixel" (bpp) refers to the sum of the bits in all three color channels and represents the total colors available at each pixel. Confusion arises frequently with color images because it may be unclear whether a posted number refers to the bits per pixel or bits per channel. Using "bpp" as a suffix helps distinguish these two terms.
bits per channel，每个颜色通道的bit depth。
bits per pixel，每像素点总共的bit depth，bpp。
一般的数码相机的bpp都是24，即每个channel有 8 bit depth。
| Bits Per Pixel | Number of Colors Available | Common Name(s) |
|---|---|---|
| 1 | 2 | Monochrome |
| 2 | 4 | CGA |
| 4 | 16 | EGA |
| 8 | 256 | VGA |
| 16 | 65536 | XGA, High Color |
| 24 | 16777216 | SVGA, True Color |
| 32 | 16777216 + Transparency | |
| 48 | 281 Trillion |
上表汇总了一些常见的名词术语。
The human eye can only discern about 10 million different colors, so saving an image in any more than 24 bpp is excessive if the only intended purpose is for viewing. On the other hand, images with more than 24 bpp are still quite useful since they hold up better under post-processing.
人眼大约只能识别1000万中颜色（已经够多了），那么bpp超过24的图片，主要是用来进行后期处理使用，并不是用来view的。(really?)
HDR10支持10bit bit-depth，DOLBY VISION支持12bit色深。（首先是12 位色深，我们在以前常常听到XX手机或者电视支持1600万色，那是因为在HDTV时期，8位色深最多可以显示1600万种颜色，而近几年，在支持10位色深的HDR10标准下，可以显示10.7 亿种颜色，但杜比视界的12位色深则更进一步，可以显示680亿种颜色，杜比视界相比HDR10能够支持更丰富的色彩显示。）
本文链接：https://cs.pynote.net/ag/image/202204033/
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