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Converting pixel value (byte) to integer value

Posted on 2003-03-30
Medium Priority
Last Modified: 2008-03-10
i have used the pixelgrabber to grab pixels. When i tried to work on the individual pixel value from the integer array i found the values were actually byte values something like  (-7697782). I tried to type cast these byte values to integer. It works for certain values but for certain values i get only negative value (like -180 for -7697782). How do i convert the pixel array values to numbers within the range 0 to 255. or else how do i get an integer RGB value of a pixel within the range 0 to 255.

Someone help me in this regard.
Question by:itmaniac
LVL 35

Accepted Solution

TimYates earned 252 total points
ID: 8235298
>  found the values were actually byte values something like  (-7697782)

This can't be a byte...it's too big...

What code are you using?  If you are loading the image with a Paletted ColorModel, then you will be getting palette entries back, not RGB colors...

Otherwise, you should have an array of int, then get the colors like:

int alpha = ( color & 0xFF000000 ) >> 24 ;
int red = ( color & 0xFF0000 ) >> 16 ;
int green = ( color & 0xFF00 ) >> 8 ;
int blue = ( color & 0xFF ) ;
LVL 30

Assisted Solution

by:Mayank S
Mayank S earned 248 total points
ID: 8236970
'byte' need not be cast to 'int'. If ever required, the conversion will be done automatically, because 'int' has more range than 'byte' and by default, 'byte' and 'short' are always converted to 'int' in expressions.

byte a = 5 ;
int b ;
b = a ; // valid - 'int' has larger storage and both are compatible types
b = ( int ) a ; // the (cast) is actually not required


Expert Comment

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Expert Comment

ID: 9735655
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

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Expert Comment

by:Mayank S
ID: 9738146
I would say: Split between TimYates and mayankeagle - their explanations are enough as per the questioner's requirements.
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Expert Comment

ID: 9738164
OK.  Thanks Mayank ;-)

Correction posted to cleanup:  Split between TimYates and mayankeagle.
LVL 30

Expert Comment

by:Mayank S
ID: 9738177
Please go ahead.

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