顏色分解到它的RGB值

Question

我寫Xlib中的一個項目，並有關於colors.I使用unsigned long型變量存儲顏色values.does問題有人知道我怎麼可以把紅，綠和藍色值每種顏色？

Answer 1

你是說顏色的24位（每個顏色分量8位）一起存儲在一個32位整數？如果是這種情況，您可以使用邏輯與操作來獲取值以清零其他位。

比方說，你開始

/* 
alpha? r g b 
00000000 10101010 10101010 10101010 your 32 bit integer might look like this 
& logical AND operator 
00000000 00000000 00000000 11111111 a bit mask 
= 
00000000 00000000 00000000 10101010 the result 
so now your 32 bit integer only has the blue values. 
To do this in code... 
*/ 
unsigned char B = (unsigned char) (your_integer & 0x000000ff) //000000ff is hex version of the bit mask 
//but now what about the other two colors? you can't just apply a bit mask like 0000ff00 because 00000000000000001010101000000000 is much larger than 255. 

//So you have to either divide the result by 256 to shift the bits right, or use >>8 to shift them to the right. 

unsigned char G = (unsigned char) ((your_integer & 0x0000ff00)/256) 
unsigned char R = (unsigned char) ((your_integer & 0x00ff0000)/256^2) 
//or using the way I've used in the past... shifting before the mask. 

unsigned char G = (unsigned char) ((your_integer >> 8) & 0x000000ff) 
unsigned char R = (unsigned char) ((your_integer >> 16) & 0x000000ff) 

Answer 2

 byte a = (byte)(value >> 24); 
     byte r = (byte)(value >> 16); 
     byte g = (byte)(value >> 8); 
     byte b = (byte)value;