从字节中获取值

本文关键字：获取 字节 | 更新日期: 2023-09-27 18:28:39

如果我有一个方法，它接收一个红色字节、一个绿色字节和一个蓝色字节，并且我知道从每个字节中提取红色字节中的最后3个比特、绿色字节中的最近2个比特和蓝色字节中的后3个比特，我将如何实现这一点？我使用了下面的代码，但它并不完全有效。我在这里做错了什么？

    private const byte InverseBlueMask = 7; // 00000111
    private const byte InverseGreenMask = 3; // 00000011
    private const byte InverseRedMask = 7; //  00000111
    //private const byte InverseBValueMask = 31; // 00011111
    //private const byte InverseGValueMask = 231; // 11100111
    //private const byte InverseRValueMask = 248; //  11111000

  public void getEachBitOfMessage(byte byteToManipulate, int colour)
    {
        byte value = 0;
        byte returnByte = 0; 

        if (colour == BLUE)
        {
            value = (byte)(byteToManipulate | BValueMask);
            value = (byte)(value >> 5);
            returnByte = (byte)(byteToManipulate | InverseBlueMask);
            returnByte = (byte)(returnByte & value);
            String theByte = returnByte.ToString(); 
        }
        else if (colour == GREEN)
        {
            value = (byte)(byteToManipulate | GValueMask);
            value = (byte)(value >> 3);
            returnByte = (byte)(byteToManipulate | InverseGreenMask);
            returnByte = (byte)(returnByte & value);
            String theByte = returnByte.ToString(); 
        }
        else if (colour == RED)
        {
            value = (byte)(byteToManipulate | RValueMask);
            returnByte = (byte)(byteToManipulate | InverseRedMask);
            returnByte = (byte)(returnByte & value);
            String theByte = returnByte.ToString(); 
        }
     }

这是我用来将消息的比特放入每个颜色字节的方法

    private const byte BlueMask = 248; // 11111000
    private const byte GreenMask = 252; // 11111100
    private const byte RedMask = 248; //  11111000
    private const byte BValueMask = 224; // 11100000
    private const byte GValueMask = 24; // 00011000
    private const byte RValueMask = 7; //  00000111

     public byte changeEachBit(byte byteToManipulate, int colour, byte theMessage)
     {
        byte value = 0;
        byte returnByte = 0; 
        if (colour == BLUE)
        {
           value= (byte)(theMessage & BValueMask);
           value = (byte)(value >> 5); 
           returnByte = (byte)(byteToManipulate & BlueMask);
           returnByte = (byte)(returnByte | value); 
        }
        else if (colour == GREEN)
        {
            value = (byte)(theMessage & GValueMask);
            value = (byte)(value >> 3);
            returnByte = (byte)(byteToManipulate & GreenMask);
            returnByte = (byte)(returnByte | value);
        }
        else if (colour == RED)
        {
            value = (byte)(theMessage & RValueMask);
            returnByte = (byte)(byteToManipulate & RedMask);
            returnByte = (byte)(returnByte | value);
        }
     }

从字节中获取值

从每个字节中，如果我提取红色字节中的最后3位，最后2位绿色字节中的位和蓝色字节中的最后3位，如何我做到了吗？

这将屏蔽除您要求的较低n位之外的所有位。

red &= 0x07;
green &= 0x03;
blue &= 0x07;

这很有效。。

    private const byte InverseBlueMask = 7; // 00000111
    private const byte InverseGreenMask = 3; // 00000011
    private const byte InverseRedMask = 7; //  00000111
    public void getEachBitOfMessage(byte byteToManipulate, int colour)
    {
        byte value = 0;
        if (countToByte == 3)
        {
            byte blueAreaInTotal = 0;
            byte greenAreaInTotal = 0;
            byte redAreaInTotal = 0;
            byte total = 0; 
            redAreaInTotal = (byte)(redCount);
            blueAreaInTotal = (byte)(blueCount << 5);
            greenAreaInTotal = (byte)(greenCount << 3);
            total = (byte)(total | redAreaInTotal); 
            total = (byte)(total | blueAreaInTotal);
            total = (byte)(total | greenAreaInTotal); 
            convertToChar(total);
            redCount = 0;
            blueCount = 0;
            greenCount = 0; 
            countToByte = 0; 
        }
        if (colour == BLUE)
        {
            value = (byte)(byteToManipulate & InverseBlueMask);
            blueCount = value; 
        }
        else if (colour == GREEN)
        {
            value = (byte)(byteToManipulate & InverseGreenMask);
            greenCount = value; 
        }
        else if (colour == RED)
        {
            value = (byte)(byteToManipulate & InverseRedMask);
            redCount = value; 
        }
        countToByte++; 
    }

private const byte BValueMask = 224; // 11100000
/* ... */
    if (colour == BLUE)
    {
        value = (byte)(byteToManipulate | BValueMask);
        value = (byte)(value >> 5);

这里的效果是打开上面的三个比特，然后扔掉下面的五个比特。你不妨写下：value = 7;。也许这三组语句的目的是使用不同的掩码，或者使用不同的位操作？

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