setPixels(int[] inData)

Posted on 2004-10-04
Medium Priority
Last Modified: 2010-03-31

Does anybody have any idea what this function does?

   void setPixels(int[] inData){
        pixel = new int[width * height];
        int index = 0;
        int red = 0;
        int green = 0;
        int blue = 0;
        for (int y = 0; y < height; y++) {
            //int red = (y * 255) / (height - 1);
            for (int x = 0; x < width; x++) {
                //green = (x * 255) / (width - 1);
                if (data!=null){
                    red = (inData[index]>>>16) & 0xFF;
                    green = (inData[index]>>>8) & 0xFF;
                    blue = (inData[index]) & 0xFF;
                pixel[index++] = (255 << 24) | (red << 16) | (green <<8) | blue;
Question by:dkim18
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LVL 92

Expert Comment

ID: 12221881
its copying an array of pixels, setting the alpha bits to 255.

Author Comment

ID: 12221968

what does this line do?
 red = (inData[index]>>>16) & 0xFF;

can you explain more in detail? or show me helpful links? I am not familiar with this pixels thing...

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LVL 92

Assisted Solution

objects earned 280 total points
ID: 12222002
LVL 21

Accepted Solution

MogalManic earned 320 total points
ID: 12222667
I'll break this  down one step at a time:
inData[index] represents an index to the array of int (each int is 32 bits)
>>> is an unsigned shift right
(inData[index]>>>16) means to take the 2nd 16 bits of data and move it into the 1st 16 bits
  (e.g 10101010101010101111111111111111 becomes 00000000000000001010101010101010101010101010101)
(inData[index]>>>16) & 0xFF means keep the 1st 16 bits and discard the rest
red = (inData[index]>>>16) & 0xFF;
   means grab the 2nd set of 16 bits (counting from the right hand side) and discard the rest and store it in the variable red

green = (inData[index]>>>8) & 0xFF;
   means grab the bits between 8 and 21
blue = (inData[index]) & 0xFF;
   means grab the 1st 16 bits

Author Comment

ID: 12223744
another quick question. Is '0xFF' compact way to specify byte values?
why do we use this format?
LVL 92

Expert Comment

ID: 12223753
they are hex values, and are handy when dealing with byte and word values.
LVL 21

Expert Comment

ID: 12225044
Each hex character represents 4 binary characters.  So to know which bits are effected by an operation, just memorize this table (or tape it to your monitor):
Hex      binary
1      0001
2      0010
3      0011
4      0100
5      0101
6      0110
7      0111
8      1000
9      1001
A      1010
B      1011
C      1100
D      1101
E      1110
F      1111

So you are right, 0xFF is a compact way of specifying 11111111

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