转:http://www.xuebuyuan.com/935987.html
背景:在我们的计算机中图像是以RGB888格式显示图像的,24位图每个像素保存了32bit的数据,即RGB888+Alpha,Alpha就是半透明填充字节……但是对于真彩的图像而言,肉眼在16bit的时候已经难以分辨了,因此,有些时候,可以讲RGB888转换为RGB565来存储,减少了存储器的容量的同时,降低了数据量;在后端显示的时候,再次把RGB565转换为RGB888,实现数据宽度的匹配!!
题记: 总的思想就是,低位增加或者移除。
一.RGB888->RGB565
方法只要提取相应单色高位即可(R5 G6 B5),但会导致低位的缺失,影响精度,而且无法恢复。
二.RGB565->RGB888
方法只要补充相应单色低位即可(R3 G2 B3)。
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | R7 | R6 | R5 | R4 | R3 | R2 | R1 | R0 | G7 | G6 | G5 | G4 | G3 | G2 | G1 | G0 | B7 | B6 | B5 | B4 | B3 | B2 | B1 | B0 |
R7 | R6 | R5 | R4 | R3 | G7 | G6 | G5 | G4 | G3 | G2 | B7 | B6 | B5 | B4 | B3 |
代码:
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#define RGB888_RED 0x00ff0000
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#define RGB888_GREEN 0x0000ff00
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#define RGB888_BLUE 0x000000ff
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#define RGB565_RED 0xf800
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#define RGB565_GREEN 0x07e0
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#define RGB565_BLUE 0x001f
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unsigned short RGB888ToRGB565(unsigned int n888Color)
-
{
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unsigned
short n565Color =
0;
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-
// 获取RGB单色,并截取高位
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unsigned
char cRed = (n888Color & RGB888_RED) >>
19;
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unsigned
char cGreen = (n888Color & RGB888_GREEN) >>
10;
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unsigned
char cBlue = (n888Color & RGB888_BLUE) >>
3;
-
-
// 连接
-
n565Color = (cRed <<
11) + (cGreen <<
5) + (cBlue <<
0);
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return n565Color;
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}
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unsigned int RGB565ToRGB888(unsigned short n565Color)
-
{
-
unsigned
int n888Color =
0;
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-
// 获取RGB单色,并填充低位
-
unsigned
char cRed = (n565Color & RGB565_RED) >>
8;
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unsigned
char cGreen = (n565Color & RGB565_GREEN) >>
3;
-
unsigned
char cBlue = (n565Color & RGB565_BLUE) <<
3;
-
-
// 连接
-
n888Color = (cRed <<
16) + (cGreen <<
8) + (cBlue <<
0);
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return n888Color;
-
}