B/W Contrast and Color Contrast the image in ImageView (Android)

Before Contrast

After Black/White Contrast

Contrast 50

Contrast 100

After Color Contrast

Contrast 100

 Create new Android Project

Project Name: PlayingwithBitmaps

Build Target: Android 2.3.3   //or greater than that

Application Name: PlayingwithBitmaps

Package Name: com.hamad.playingwithbitmaps

Create Activity: Main

Min SDK: 10 // or greater than that

  1.create main layout:

• One image view to display the image.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    android:id="@+id/rlMain" >

    <ImageView
        android:id="@+id/imViewAndroid"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:src="@drawable/beautiful" />

</RelativeLayout>

 2. code of main activity:

package com.shaikhhamadali.blogspot.playingwithbitmaps;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.widget.ImageView;

public class Main extends Activity {
 ImageView imViewAndroid;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  imViewAndroid = (ImageView) findViewById(R.id.imViewAndroid);
  imViewAndroid.setImageBitmap(takeContrast(BitmapFactory.decodeResource(getResources(), R.drawable.android_droid),100));
 }

 public  Bitmap takeContrast(Bitmap src, double value) {
  // src image size
  int width = src.getWidth();
  int height = src.getHeight();
  // create output bitmap with original size
  Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
  // color information
  int A, R, G, B;
  int pixel;
  // get contrast value
  double contrast = Math.pow((100 + value) / 100, 2);

  // scan through all pixels
  for(int x = 0; x < width; ++x) {
   for(int y = 0; y < height; ++y) {
    // get pixel color
    pixel = src.getPixel(x, y);
    A = Color.alpha(pixel);
    // apply filter contrast for every channel R, G, B
    R = Color.red(pixel);
    R = (int)(((((R / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
    if(R < 0) { R = 0; }
    else if(R > 255) { R = 255; }

    G = Color.red(pixel);
    G = (int)(((((G / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
    if(G < 0) { G = 0; }
    else if(G > 255) { G = 255; }

    B = Color.red(pixel);
    B = (int)(((((B / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
    if(B < 0) { B = 0; }
    else if(B > 255) { B = 255; }

    // set new pixel color to output bitmap
    bmOut.setPixel(x, y, Color.argb(A, R, G, B));
   }
  }

  // return final image
  return bmOut;
 }
 public  Bitmap takeColorContrast(Bitmap src, double value) {
  // src image size
  int width = src.getWidth();
  int height = src.getHeight();
  // create output bitmap with original size
  Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
  // color information
  int A, R, G, B;
  int pixel;
  // get contrast value
  double contrast = Math.pow((100 + value) / 100, 2);

  // scan through all pixels
  for(int x = 0; x < width; ++x) {
   for(int y = 0; y < height; ++y) {
    // get pixel color
    pixel = src.getPixel(x, y);
    A = Color.alpha(pixel);
    // apply filter contrast for every channel R, G, B
    R = Color.red(pixel);
    R = (int)(((((R / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
    if(R < 0) { R = 0; }
    else if(R > 255) { R = 255; }

    G = Color.green(pixel);
    G = (int)(((((G / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
    if(G < 0) { G = 0; }
    else if(G > 255) { G = 255; }

    B = Color.blue(pixel);
    B = (int)(((((B / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
    if(B < 0) { B = 0; }
    else if(B > 255) { B = 255; }

    // set new pixel color to output bitmap
    bmOut.setPixel(x, y, Color.argb(A, R, G, B));
   }
  }

  // return final image
  return bmOut;
 }
}

  Steps:

1. Calculate contrast value: contrast = ((value + 100) / 100) ^ 2 (square by 2, or power 2).
2. Repeat this for each color channel:

•  Take pixel color divided by 255
•  Minus 0.5
•  Multiply contrast value calculated above.
•  Plus 0.5
•  Multiply by 255

  3. note that:

• Refer to these Wiki pages on Contrast images to get the concepts and ideas:Contrast(Vision) | Image Editing – Contrast.
• With the help of this,takeContrast() method you can set the B/W Contrast of image on click,on action_down etc
• With the help of this,takeColorContrast() method you can set the Color Contrast of image on click,on action_down etc

  4. conclusion:

• Some deep information about b/w contrast and color contrast.
• Know how to set b/w contrast and color contrast of an image bitmap from drawables.

  5. About the post:

•  The code seems to explain itself due to comments, and is very easy to understand.
•  Don’t mind to write a comment whatever you like to ask, to know,to suggest or recommend.
•  Hope you enjoy it!

6. Source Code:

        you can download the source code here

Cheers,

Hamad Ali Shaikh