Converting simple image to greyscale

Question

I am trying to convert a normal colored image to greyscale image.Code is really simple but don't know why I am getting error.I am just changing color value pixel by pixel and then storing it in the new bitmap.Error is coming when I am trying to set pixels to the new bitmap. ``` Bitmap c=BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getAbsolutePath() + "/1.jpg"); int width=c.getWidth(); int height=c.getHeight(); int A,B,R,G; int pixel; for(int x = 0; x < width; x++) { for(int y = 0; y < height; y++) { // get one pixel color // pixel = c.getPixel(x, y); // retrieve color of all channels // A = Color.alpha(c.getPixel(x, y)); R = Color.red(c.getPixel(x, y)); G = Color.green(c.getPixel(x, y)); B = Color.blue(c.getPixel(x, y)); // take conversion up to one single value R = G = B = (int)(0.299 * R + 0.587 * G + 0.114 * B); // set new pixel color to output bitmap h=String.valueOf(R); bmOut.isMutable(); bmOut.setPixel(x, y, Color.argb(Color.alpha(c.getPixel(x, y)), R, G, B…

Accepted Answer

I found two ways while I was trying to achieve the same.

Using `ColorMatrix`

```
private Bitmap androidGrayScale(final Bitmap bmpOriginal) {
    int width, height;
    height = bmpOriginal.getHeight();
    width = bmpOriginal.getWidth();
    Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bmpGrayscale);
    Paint paint = new Paint();
    ColorMatrix colorMatrix = new ColorMatrix();
    colorMatrix.setSaturation(0);
    ColorMatrixColorFilter colorMatrixFilter = new ColorMatrixColorFilter(colorMatrix);
    paint.setColorFilter(colorMatrixFilter);
    canvas.drawBitmap(bmpOriginal, 0, 0, paint);
    return bmpGrayscale;
}
```

Using `OpenCV`

Download `OpenCV` Library And Import as a Library Project. Add this library to your project as a reference library.

Download Links : OpenCV

```
private Bitmap openCVGrayScale(final Bitmap bmpOriginal, final String filePath) {
        Mat imgToProcess;
        Mat imgToDest = new Mat();
        imgToProcess = Highgui.imread(filePath, Highgui.CV_LOAD_IMAGE_GRAYSCALE);
        org.opencv.android.Utils.bitmapToMat(bmpOriginal, imgToProcess);
        Imgproc.cvtColor(imgToProcess, imgToDest, Imgproc.COLOR_BGR2GRAY);
        Bitmap bmpGrayscale = Bitmap.createBitmap(imgToDest.cols(), imgToDest.rows(), Bitmap.Config.ARGB_8888); 
        org.opencv.android.Utils.matToBitmap(imgToDest, bmpGrayscale);
        return bmpGrayscale;
    }
```

Do not forget to check in your `Activity`

```
static {
    if (!OpenCVLoader.initDebug()) {
        android.util.Log.e("TAG", "Error");
    }
}
```

Thanks.

Converting simple image to greyscale

Solution

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