c ++定义了16bit（高）的颜色 [英] c++ defined 16bit (high) color

问题描述

我正在开发一个带有TFT触摸屏的项目，这个屏幕上有一个附带的库。但在一些阅读后，我仍然没有得到什么。在库中有关于颜色的一些定义：

I am working on a project with a TFT touch screen, with this screen there is an included library. But after some reading, i still dont get something. In the library there are some defines regarding colors:

/* some RGB color definitions                                                 */
#define Black           0x0000      /*   0,   0,   0 */
#define Navy            0x000F      /*   0,   0, 128 */
#define DarkGreen       0x03E0      /*   0, 128,   0 */
#define DarkCyan        0x03EF      /*   0, 128, 128 */
#define Maroon          0x7800      /* 128,   0,   0 */
#define Purple          0x780F      /* 128,   0, 128 */
#define Olive           0x7BE0      /* 128, 128,   0 */
#define LightGrey       0xC618      /* 192, 192, 192 */
#define DarkGrey        0x7BEF      /* 128, 128, 128 */
#define Blue            0x001F      /*   0,   0, 255 */
#define Green           0x07E0      /*   0, 255,   0 */
#define Cyan            0x07FF      /*   0, 255, 255 */
#define Red             0xF800      /* 255,   0,   0 */
#define Magenta         0xF81F      /* 255,   0, 255 */
#define Yellow          0xFFE0      /* 255, 255,   0 */
#define White           0xFFFF      /* 255, 255, 255 */
#define Orange          0xFD20      /* 255, 165,   0 */
#define GreenYellow     0xAFE5      /* 173, 255,  47 */
#define Pink                        0xF81F

这些是16位颜色。但是他们如何从：0,128,128（深蓝色）到0x03EF。我的意思是，你如何将16位颜色转换为uint16？这不需要在代码中有anwser，因为我只是想在库中添加一些collors。到一个在线转换器的链接（我找不到）也可以：）

Those are 16 bit colors. But how do they go from: 0,128,128(dark cyan) to 0x03EF. I mean, how do you convert a 16bit color to a uint16? this doesn't need to have a anwser in code, because i just want to add some collors in the library. A link to a online converter (wich i could not find) would be okay as well :)

感谢

推荐答案

从这些可以很容易地找出公式：

From these one can easily find out the formula:

#define Red             0xF800      /* 255,   0,   0 */  
#define Magenta         0xF81F      /* 255,   0, 255 */
#define Yellow          0xFFE0      /* 255, 255,   0 */

F800设置了5个MSB位，FFE0没有设置5个LSB。
0xF81F显然具有5个LSB和5个MSB的集合，这证明格式是RGB565。

F800 has 5 MSB bits set and FFE0 has 5 LSB not set. 0xF81F has obviously both 5 LSB's and 5 MSB's set, which proves the format to be RGB565.

将值173转换为Red的公式不是直接的，因为它可能看起来 - 你不能简单地删除3个最低有效位，但必须线性插值使255对应于31（或绿色255对应于63）。

The formula to convert a value 173 to Red is not as straightforward as it may look -- you can't simply drop the 3 least significant bits, but have to linearly interpolate to make 255 to correspond to 31 (or green 255 to correspond to 63).

NewValue = (31 * old_value) / 255;

（这只是一个截断的部分 - 可能需要适当的舍入）

(And this is still just a truncating division -- proper rounding could be needed)

适当舍入和缩放：

Uint16_value = (((31*(red+4))/255)<<11) | 
               (((63*(green+2))/255)<<5) | 
               ((31*(blue+4))/255);

EDIT 添加括号，以符合JasonD的建议。

EDIT Added parenthesis to as helpfully suggested by JasonD.

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