How to programmatically change contrast of a bitmap in android?

Question

I want to programmatically change the contrast of bitmap. Till now I have tried this.

private Bitmap adjustedContrast(Bitmap src, double value)
    {
        // image size
        int width = src.getWidth();
        int height = src.getHeight();
        // create output bitmap
        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 bmOut;
    }

But this does not work as expected. Please help me in this or provide any other solution to achieve this. Thanks in advance.

what doesn't work as expected? please elaborate more detailed what does work and what doesnt. — devsnd, Oct 15 '12 at 08:11

score 66 · Answer 1 · answered Jul 26 '13 at 17:36

66

Here is complete method:

/**
 * 
 * @param bmp input bitmap
 * @param contrast 0..10 1 is default
 * @param brightness -255..255 0 is default
 * @return new bitmap
 */
public static Bitmap changeBitmapContrastBrightness(Bitmap bmp, float contrast, float brightness)
{
    ColorMatrix cm = new ColorMatrix(new float[]
            {
                contrast, 0, 0, 0, brightness,
                0, contrast, 0, 0, brightness,
                0, 0, contrast, 0, brightness,
                0, 0, 0, 1, 0
            });

    Bitmap ret = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());

    Canvas canvas = new Canvas(ret);

    Paint paint = new Paint();
    paint.setColorFilter(new ColorMatrixColorFilter(cm));
    canvas.drawBitmap(bmp, 0, 0, paint);

    return ret;
}

answered Jul 26 '13 at 17:36

Ruslan Yanchyshyn

2,774
1
24
22

1

This's the fastest solution I found so far. Probably only a renderscript-based one would be faster... – Aron Lorincz Feb 15 '14 at 08:34
Awesome, this method processes my image in about a second, above method took about 20 seconds. – Gusten Feb 21 '14 at 08:06
1

what is the max & min value of contrast & brightness. I use -255 t0 255 for brightness & -100 to 100 for contrast, but i get wrong result. I also try to use value 0 for contrast while some value for brightness i get a black image.Please help me. I got this is the fastest method, but it give me wrong result, definitely i do something wrong, it would be nice if any one correct me. – mnsalim May 02 '14 at 16:46
Just a improvement to the code due to the constant break on the bmp.getConfig... Bitmap.Config config = src.getConfig(); if (config == null) { config = Bitmap.Config.ARGB_8888; } Bitmap ret = Bitmap.createBitmap(src.getWidth(), src.getHeight(), config); – vianna77 Nov 10 '15 at 01:42
This will create OutOfMemmory if we are changing the brightness through silder – V I J E S H Aug 29 '17 at 09:54

score 24 · Accepted Answer · 2012-10-15T08:54:45.223

Try this. Your code didn't work because you create only a mutable bitmap and didn't copy the image of source bitmap to the mutable one if i'm not mistaken.

Hope It helps :)

private Bitmap adjustedContrast(Bitmap src, double value)
{
    // image size
    int width = src.getWidth();
    int height = src.getHeight();
    // create output bitmap

    // create a mutable empty bitmap
    Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());

    // create a canvas so that we can draw the bmOut Bitmap from source bitmap
    Canvas c = new Canvas();
    c.setBitmap(bmOut);

    // draw bitmap to bmOut from src bitmap so we can modify it
    c.drawBitmap(src, 0, 0, new Paint(Color.BLACK));


    // 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 bmOut;
}

Thanks, but I don't think we need a `Canvas` here -- we're writing to the bitmap `bmOut` directly. — Vasiliy Kulakov, Feb 17 '15 at 19:08
what is max and min values can update your answer with this values — Kishan Donga, Jul 24 '20 at 05:14

score 8 · Answer 3 · edited Nov 23 '16 at 11:10

We can use seek bar to adjust contrast.

MainActivity.java:

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.graphics.Paint;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    ImageView imageView;
    SeekBar seekbar;
    TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = (ImageView) findViewById(R.id.image);
        textView = (TextView) findViewById(R.id.label);

        seekbar = (SeekBar) findViewById(R.id.seekbar);
        seekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean b) {
                imageView.setImageBitmap(changeBitmapContrastBrightness(BitmapFactory.decodeResource(getResources(), R.drawable.lhota), (float) progress / 100f, 1));
                textView.setText("Contrast: "+(float) progress / 100f);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {}

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {}
        });

        seekbar.setMax(200);
        seekbar.setProgress(100);
    }

    public static Bitmap changeBitmapContrastBrightness(Bitmap bmp, float contrast, float brightness) {
        ColorMatrix cm = new ColorMatrix(new float[]
                {
                        contrast, 0, 0, 0, brightness,
                        0, contrast, 0, 0, brightness,
                        0, 0, contrast, 0, brightness,
                        0, 0, 0, 1, 0
                });

        Bitmap ret = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());

        Canvas canvas = new Canvas(ret);

        Paint paint = new Paint();
        paint.setColorFilter(new ColorMatrixColorFilter(cm));
        canvas.drawBitmap(bmp, 0, 0, paint);

        return ret;
    }
}

activity_main.java:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/image"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/label"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="8dp"
        android:textAppearance="@android:style/TextAppearance.Holo.Medium" />

    <SeekBar
        android:id="@+id/seekbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

score 7 · Answer 4 · edited Jun 23 '22 at 08:07

Assumption - ImageView is used to display the bitmap

I did a more enhancement in the Ruslan's answer

Instead of replacing bitmap every time (which makes it slow if you are using seek bar) we can work on the Color Filter of the ImageView.

float contrast;
float brightness = 0;
ImageView imageView;

// SeekBar ranges from 0 to 90
// contrast ranges from 1 to 10  
mSeekBarContrast.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
            contrast = (float) (i + 10) / 10;
            // Changing the contrast of the bitmap
            imageView.setColorFilter(getContrastBrightnessFilter(contrast,brightness));
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }
});

ColorMatrixColorFilter getContrastBrightnessFilter(float contrast, float brightness) {
    ColorMatrix cm = new ColorMatrix(new float[]
            {
                    contrast, 0, 0, 0, brightness,
                    0, contrast, 0, 0, brightness,
                    0, 0, contrast, 0, brightness,
                    0, 0, 0, 1, 0
            });
    return new ColorMatrixColorFilter(cm);
}

P.S - Brightness can also be changed along with contrast using this method

This is best method to make contrast and brightness to the image. It works faster then other tools. Thank you so much — M DEV, Jun 15 '22 at 12:37
now, it is working very fine. If we seek back from 50 then the image gets dark and if we seek more from 50 then image gets bright. — M DEV, Jun 15 '22 at 13:00

Patrick · Answer 5 · 2023-08-10T10:46:02.593

6

Update 2023: Since Renderscript is deprecated since Android 12, this solution is not recommended anymore.

Here is a Renderscript implementation (from the Gradle Example Projects)

ip.rsh

#pragma version(1)
#pragma rs java_package_name(your.app.package)

contrast.rs

#include "ip.rsh"

static float brightM = 0.f;
static float brightC = 0.f;

void setBright(float v) {
    brightM = pow(2.f, v / 100.f);
    brightC = 127.f - brightM * 127.f;
}

void contrast(const uchar4 *in, uchar4 *out)
{
#if 0
    out->r = rsClamp((int)(brightM * in->r + brightC), 0, 255);
    out->g = rsClamp((int)(brightM * in->g + brightC), 0, 255);
    out->b = rsClamp((int)(brightM * in->b + brightC), 0, 255);
#else
    float3 v = convert_float3(in->rgb) * brightM + brightC;
    out->rgb = convert_uchar3(clamp(v, 0.f, 255.f));
#endif
}

Java

private Bitmap changeBrightness(Bitmap original RenderScript rs) {
    Allocation input = Allocation.createFromBitmap(rs, original);
    final Allocation output = Allocation.createTyped(rs, input.getType());
    ScriptC_contrast mScript = new ScriptC_contrast(rs);
    mScript.invoke_setBright(50.f);
    mScript.forEach_contrast(input, output);
    output.copyTo(original);
    return original;
}

edited Aug 10 '23 at 10:46

answered Apr 19 '14 at 16:47

Patrick

33,984
10
106
126

Can you post more completed example? – Andrew F Jan 25 '16 at 15:54
1

the sample is pretty complete, for integrating it see the link, bottom of the page with full projects – Patrick Jan 25 '16 at 15:57
anyway can you post direct link to full project? :) I found only one link and it's unavailable – Andrew F Jan 25 '16 at 16:01
They seem to have removed the link to the projects, just search how to create an app with renderscript, the rest should be clear – Patrick Jan 25 '16 at 16:10
RenderScript APIs are deprecated starting in Android 12 – Md. Yamin Mollah May 16 '23 at 15:48

tobalr · Answer 6 · 2016-11-23T21:16:25.577

I just had the same problem and ended up using the Color Matrix that Ruslan Yanchyshyn describes. I needed to automatically adjust brightness depending on the image, so I used BoofCV to create a histogram from a scaled version of the image - It took way to long to process the whole image. Then I analyzed the histogram - looked at what was the darkest and brightest colors and then created a color matrix which transforms the colors so the darkest colors are 0 and the brightest colors are 255. In this way the new image uses the whole spectrum from dark/black to light/white now.

Ended up writing a small post on how I did it on our company blog here if anyone are interested. http://appdictive.dk/blog/projects/2016/07/26/levels_with_color_matrix/

kdroider · Answer 7 · 2012-10-15T08:19:39.743

1

Maybe you can try this one:

http://xjaphx.wordpress.com/2011/06/21/image-processing-contrast-image-on-the-fly/

Hope that helps! :)

edited Oct 15 '12 at 08:19

answered Oct 15 '12 at 08:08

kdroider

731
5
20

Thanks for your reply. I tried this. But this code works with canvas only and I cannot retrieve the changed image from canvas. So is there any other way for it. – Sanchit Paurush Oct 15 '12 at 08:11
I edited the link above. I hope that will be more helpful in your case. :) – kdroider Oct 15 '12 at 08:20
It is the same code that I gave above. It always make my image black and white and does not make it back to its original colors. Please provide any other. – Sanchit Paurush Oct 15 '12 at 08:30

score 1 · Answer 8 · answered Oct 15 '12 at 08:57

1

http://android.okhelp.cz/bitmap-set-contrast-and-brightness-android/

have a look at this ,this might solve your problem

answered Oct 15 '12 at 08:57

Amit Hooda

2,133
3
23
37

How to programmatically change contrast of a bitmap in android?

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