如何在Android中获取图像的像素值在0-255范围内

Question

I am trying to modify the image which I take it from the gallery in android. For modifying I need to get the pixel value of the image.

I do not want to differentiate the pixel value into R,G,B value. I want the pixel value as a single value

                              for (x = 0; x < w; x++){
                for (y = 0;y < w; y++){
                int pixels = bmpimg1.getPixel(x, y);
                int alphavalue=Color.alpha(pixels);
                int redValue = Color.red(pixels);
                int blueValue = Color.blue(pixels);
                int greenValue = Color.green(pixels);
                 totalvalue[x][y]=(redvalue+bluevalue+greenvalue)/3
                         }
                         }

//totalvalue=Assuming addition of redvalue, bluevalue,greenvalue and taking average will give me the pixel value in that location//

When I try to recreate the image using the totalvalue, I am not getting the image which i gave it as input.

I did the same in java using Raster.getpixels, when I tried to create the same image I am able to get the same image.

              Bufferedimage img=ImageIO.read(new File("a.jpg");
              Raster raster=img.getData();
              for (int x=0;x<w;x++)
        {
            for(int y=0;y<h;y++)
            {
                pixels[x][y]=raster.getSample(x,y,0);
                pixel[count++]=pixels[x][y];
            }
        }

When I create a new image using bufferedImage with the pixel[x][y], I am getting the original image

But in android, getpixel gives values in negative number

So how can i get the values of each pixel in the range 0-255 without separating into RGB value.

Kindly help me with this problem. Thank you

Answer 1

Since all red, blue and green component can take values up to 255, you can't just sum them to get a unic color value (since 1+2+3 = 2+3+1 for example)

you will have to store the color value in a number bigger than 255 with the method

color = redValue*2^16 + greenValue*2^8 + blueValue

You should be able to figure out how to retrieve red blue and green from this unique value

Good luck