How to get pixels of an image in res folder of an android project

Question

new to android. I don't think any of the questions on here are the same as mine.

I have images loaded into my res folder. I put them into a drawable folder. How can I get the pixels of an image named bb.png in the res.drawable folder?

I will need a simple explanation on how to get the image file into a variable, and what 'getPixel(...)' command I will need to use. I don't need to display the image, just get the pixel array from it, and check if the pixel is black or white. Any help is appreciated, thanks!

Mike

Answer 1

It's actually really easy!

Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.image);

Once, you have a Bitmap object, there's a couple of options.

bm.getPixel(x,y) will return an int that corresponds to an int in the Color class, such as Color.BLACK or Color.WHITE.

Additionally, bm.copyPixelsToBuffer(Buffer destination) will copy all of the pixels into a Buffer object, which you could search pixel-by-pixel.

Check out the documentation for further details.

Bitmap Documentation

Color Documentation

Here is a sample snippet of code, assuming that you have an image in your /res/drawable folder called 'image'.

Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.image);
int pixelColor = bm.getPixel(10,10); //Get the pixel at coordinates 10,10

if(pixelColor == Color.BLACK) {
  //The pixel is black
}

else if(pixelColor == Color.WHITE) {
  //The pixel was white
}

Obviously, you should be careful about getting pixels. Make sure the pixel exists, and that the coordinate is not bigger than the image. To get the dimensions of a Bitmap, simply use bm.getHeight() and bm.getWidth(), respectively.