how to read RGB Data from png in j2me

Question

hey i have using j2me to read an image

i want to do some process on that image like Darkenes , lightens

i already read image as an input stream

        InputStream iStrm = getClass().getResourceAsStream("/earth.PNG");
         ByteArrayOutputStream bStrm = new ByteArrayOutputStream();

       int ch;

  while ((ch = iStrm.read()) != -1){
    bStrm.write(ch);


    byte imageData[] = bStrm.toByteArray();
   Image im = Image.createImage(imageData, 0, imageData.length);

how can i get RGB values or how can i add some values to the array of pixles
imageData[] so it can more lightens or darkness ,

is there header data including in the input stream i had read , that cause me error when iam adding some values to it ?

Answer 1

I think you should be able to do the following:

int width = im.getWidth();
int height = im.getHeight();
int[] rgbData = new int[width*height]; // since we are working with rgba

im.getRGB(rgbData, 0, width, 0, 0, width, height);

// now, the data is stored in each integer as 0xAARRGGBB, 
// so high-order bits are alpha channel for each integer

Now, if you want to put them into three arrays, one for each channel, you could do the following:

int red[][] = new int[width][height];
int green[][] = new int[width][height];
int blue[][] = new int[width][height];

for (int i = 0; i < width; i++)
{
  for (int j = 0; j < height; j++)
  {
    red[i][j] = rgb[i*width + j] & 0xFF0000;
    green[i][j] = rgb[i*width + j] & 0xFF00;
    blue[i][j] = rgb[i+width + j] & 0xFF;
  }
}

Answer 2

thanks alot

but can you help me how to sepearte each channel in array

i have problems how to read argb and with shift

Answer 3

i have try it

but i have some problems with values of red , green and blue

it is more than 255 such than 65280

and how i can i redraw iamge using red and green and blue

after i add some values to them ;