Alter blue values of a pixel

Hi Guys
I am doing a project on Steganography.I am at a juncture where I need to alter the blue values of a pixel.I have almost devised an algorithm but it is incomplete.The steps are
1)Obtain the rgb values of the pixel using getRGB and the do the right shifting and bitwise AND-ing with 0xff.
2)We will obtain integer RGB values.Change the blue to the desired value
3)Now obtain the binary equivalent of the value by left shifting and bitwise AND-ing with 0xff.

My question is how do I combine the RGB values so that I can use the setRGB method in BufferedImage.I am unable to bridge the gap.I hope I have been able to express myself clearly.I would welcome any other algorithm.Please help.I will be really grateful

Quote:

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Originally Posted by forwardbias

Hi Guys
I am doing a project on Steganography.I am at a juncture where I need to alter the blue values of a pixel.I have almost devised an algorithm but it is incomplete.The steps are
1)Obtain the rgb values of the pixel using getRGB and the do the right shifting and bitwise AND-ing with 0xff.
2)We will obtain integer RGB values.Change the blue to the desired value
3)Now obtain the binary equivalent of the value by left shifting and bitwise AND-ing with 0xff.

My question is how do I combine the RGB values so that I can use the setRGB method in BufferedImage.I am unable to bridge the gap.I hope I have been able to express myself clearly.I would welcome any other algorithm.Please help.I will be really grateful

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If you ony want to change the lowest bit of the blue value there is no need to unravel the rgb number; the following will do fine:

Code:

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int setLowestBit(int argb, boolean bit) {
  return (argb&-2)|(bit?1:0);
}

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kind regards,

Jos (bit fiddler ;-)

Thank You for replying
I might have to change the complete value in some cases based on an input.

Quote:

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Originally Posted by forwardbias

Thank You for replying
I might have to change the complete value in some cases based on an input.

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For the blue component (the least significant byte) of an argb value it's easy:

Code:

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int getValue(int argb) { return argb&0xff; }
int setValue(int argb, int val) { argb= (argb&0xffffff00)|val; return argb; }

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Two oneliners, that's all that's needed ;-)

kind regards,

Jos

Thank You