Last article "Convert bitmap from color to GrayScale" by calculation. It's another approach using ColorMatrixColorFilter. ColorMatrix is a 5x4 matrix for transforming the color+alpha components of a Bitmap. The method setSaturation() set the matrix to affect the saturation of colors. A value of 0 maps the color to gray-scale. ColorMatrixColorFilter create a colorfilter that transforms colors through a 4x5 color matrix. In the sample code below, getGrayscale_ColorMatrixColorFilter() method use ColorMatrixColorFilter with ColorMatrix of Saturation 0, to convert color bitmap to gray scale. We can also create our own matrix for ColorMatrixColorFilter to convert transform bitmap color+alpha, as shown in getGrayscale_custom_matrix() method. package com.AndroidBitmapProcessing; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.ColorMatrix; import android.graphics.ColorMatrixColorFilter; import android.graphics.Paint; import android.os.Bundle; import android.widget.ImageView; public class AndroidBitmapProcessingActivity extends Activity { ImageView imageView_Source, imageView_Gray, imageView_Gray2; Bitmap bitmap_Source, bitmap_Dest; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imageView_Source = (ImageView)findViewById(R.id.source); imageView_Gray = (ImageView)findViewById(R.id.imageGray); imageView_Gray2 = (ImageView)findViewById(R.id.imageGray2); bitmap_Source = BitmapFactory.decodeResource(getResources(), R.drawable.testpicture); imageView_Gray.setImageBitmap(getGrayscale_ColorMatrixColorFilter(bitmap_Source)); imageView_Gray2.setImageBitmap(getGrayscale_custom_matrix(bitmap_Source)); } private Bitmap getGrayscale_ColorMatrixColorFilter(Bitmap src){ int width = src.getWidth(); int height = src.getHeight(); Bitmap dest = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565); Canvas canvas = new Canvas(dest); Paint paint = new Paint(); ColorMatrix colorMatrix = new ColorMatrix(); colorMatrix.setSaturation(0); //value of 0 maps the color to gray-scale ColorMatrixColorFilter filter = new ColorMatrixColorFilter(colorMatrix); paint.setColorFilter(filter); canvas.drawBitmap(src, 0, 0, paint); return dest; } private Bitmap getGrayscale_custom_matrix(Bitmap src){ int width = src.getWidth(); int height = src.getHeight(); //Custom color matrix float[] matrix = new float[]{ 0.3f, 0.59f, 0.11f, 0, 0, 0.3f, 0.59f, 0.11f, 0, 0, 0.3f, 0.59f, 0.11f, 0, 0, 0, 0, 0, 1, 0,}; Bitmap dest = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565); Canvas canvas = new Canvas(dest); Paint paint = new Paint(); ColorMatrixColorFilter filter = new ColorMatrixColorFilter(matrix); paint.setColorFilter(filter); canvas.drawBitmap(src, 0, 0, paint); return dest; } }

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