Monday, July 19, 2010

Skew bitmap image, using Matrix

To generate a skewed bitmap, Matrix.postSkew() can be used.

Skew bitmap image, using Matrix

Extend the last exercisse "Rotate bitmap image, using Matrix".

Modify main.xml to add two SeekBar to set the skew for x and y.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
/>
<Spinner
android:id="@+id/scale"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
<SeekBar
android:id="@+id/rotate"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_margin="5px"
android:max="360"
android:progress="0"
/>
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
>
<LinearLayout
android:orientation="vertical"
android:layout_height="wrap_content"
android:layout_width="0dip"
android:layout_weight="1"
android:layout_margin="5px"
>
<TextView
android:id="@+id/textskewx"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:textSize="10px"
android:text="Skew-X: 0"
/>
<SeekBar
android:id="@+id/skewx"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:max="200"
android:progress="100"
/>
</LinearLayout>
<LinearLayout
android:orientation="vertical"
android:layout_height="wrap_content"
android:layout_width="0dip"
android:layout_weight="1"
android:layout_margin="5px"
>
<TextView
android:id="@+id/textskewy"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:textSize="10px"
android:text="Skew-Y: 0"
/>
<SeekBar
android:id="@+id/skewy"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:max="200"
android:progress="100"
/>
</LinearLayout>
</LinearLayout>
<ImageView
android:id="@+id/imageview"
android:layout_gravity="center"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:scaleType="center"
/>
</LinearLayout>


AndroidBitmap.java
package com.exercise.AndroidBitmap;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.SeekBar;
import android.widget.Spinner;
import android.widget.TextView;

public class AndroidBitmap extends Activity {

private final String imageInSD = "/sdcard/er.PNG";

ImageView myImageView;
Spinner spinnerScale;
SeekBar seekbarRotate;
SeekBar seekbarSkewX, seekbarSkewY;
TextView textSkewX, textSkewY;

private static final String[] strScale
= {"0.2x", "0.5x", "1.0x", "2.0x", "5.0x"};
private static final Float[] floatScale
= {0.2F, 0.5F, 1F, 2F, 5F};
private final int defaultSpinnerScaleSelection = 2;

private ArrayAdapter<String> adapterScale;

private float curScale = 1F;
private float curRotate = 0F;
private float curSkewX = 0F;
private float curSkewY = 0F;

Bitmap bitmap;
int bmpWidth, bmpHeight;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

myImageView = (ImageView)findViewById(R.id.imageview);

spinnerScale = (Spinner)findViewById(R.id.scale);
seekbarRotate = (SeekBar)findViewById(R.id.rotate);
seekbarSkewX = (SeekBar)findViewById(R.id.skewx);
seekbarSkewY = (SeekBar)findViewById(R.id.skewy);
textSkewX = (TextView)findViewById(R.id.textskewx);
textSkewY = (TextView)findViewById(R.id.textskewy);

adapterScale = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, strScale);
adapterScale.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerScale.setAdapter(adapterScale);
spinnerScale.setSelection(defaultSpinnerScaleSelection);
curScale = floatScale[defaultSpinnerScaleSelection];

bitmap = BitmapFactory.decodeFile(imageInSD);
bmpWidth = bitmap.getWidth();
bmpHeight = bitmap.getHeight();

drawMatrix();

spinnerScale.setOnItemSelectedListener(spinnerScaleOnItemSelectedListener);
seekbarRotate.setOnSeekBarChangeListener(seekbarRotateSeekBarChangeListener);
seekbarSkewX.setOnSeekBarChangeListener(seekbarSkewXSeekBarChangeListener);
seekbarSkewY.setOnSeekBarChangeListener(seekbarSkewYSeekBarChangeListener);
}

private void drawMatrix(){

Matrix matrix = new Matrix();
matrix.postScale(curScale, curScale);
matrix.postRotate(curRotate);
matrix.postSkew(curSkewX, curSkewY);

Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0, bmpWidth, bmpHeight, matrix, true);
myImageView.setImageBitmap(resizedBitmap);

}

private SeekBar.OnSeekBarChangeListener seekbarSkewYSeekBarChangeListener
= new SeekBar.OnSeekBarChangeListener() {

@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}

@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
curSkewY = (float)(progress-100)/100;
textSkewY.setText("Skew-Y: " + String.valueOf(curSkewY));
drawMatrix();
}
};

private SeekBar.OnSeekBarChangeListener seekbarSkewXSeekBarChangeListener
= new SeekBar.OnSeekBarChangeListener(){

@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
curSkewX = (float)(progress-100)/100;
textSkewX.setText("Skew-X: " + String.valueOf(curSkewX));
drawMatrix();
}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}};

private SeekBar.OnSeekBarChangeListener seekbarRotateSeekBarChangeListener
= new SeekBar.OnSeekBarChangeListener(){

@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// TODO Auto-generated method stub
curRotate = (float)progress;
drawMatrix();
}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}};

private Spinner.OnItemSelectedListener spinnerScaleOnItemSelectedListener
= new Spinner.OnItemSelectedListener(){

@Override
public void onItemSelected(AdapterView<?> arg0, View arg1,
int arg2, long arg3) {
// TODO Auto-generated method stub
curScale = floatScale[arg2];
drawMatrix();
}

@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
spinnerScale.setSelection(defaultSpinnerScaleSelection);
curScale = floatScale[defaultSpinnerScaleSelection];
}};
}


Download the files.

next: Generate a mirror image using Matrix.postConcat()



6 comments:

GrAde said...

This is a great Tutorial.
Could you tell me how you would add a seekbar to position the image on the horizontal.
I have tried addding postTranslate but it doesnt seem to work.
Any ideas?

Android Er said...

Hello GrAde,

I can't catch your question! Do you means move the image position using a seekbar?

J said...

What license (if any) is this code covered by? I have learned loads from it, but can I cut-and-paste some of the code or do I have to re-create it all? Thanks.

Android Er said...

Hello J,

The code is created by myself, no any license. You can use it freely, better to have a link to my blog. Thx.

Raghu said...

Hello sir,

When i run this code on the emulator its throwing an error called Force close.Please help meh........out

Berebootboy said...

Raghu make sure the SDcard link is correct and it is pointing to a picture ther