Skew bitmap image, using Matrix

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




Modify main.xml to add two SeekBar to set the skew for x and y.

  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="@string/hello"
  />
  android:id="@+id/scale"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  />
  android:id="@+id/rotate"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:layout_margin="5px"
  android:max="360"
  android:progress="0"
  />
  android:orientation="horizontal"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  >
android:orientation="vertical"
  android:layout_height="wrap_content"
  android:layout_width="0dip"
  android:layout_weight="1"
  android:layout_margin="5px"
>
  android:id="@+id/textskewx"
  android:layout_height="wrap_content"
  android:layout_width="fill_parent"
  android:textSize="10px"
  android:text="Skew-X: 0"
  />
  android:id="@+id/skewx"
  android:layout_height="wrap_content"
  android:layout_width="fill_parent"
  android:max="200"
  android:progress="100"
  />

android:orientation="vertical"
  android:layout_height="wrap_content"
  android:layout_width="0dip"
  android:layout_weight="1"
  android:layout_margin="5px"
>
  android:id="@+id/textskewy"
  android:layout_height="wrap_content"
  android:layout_width="fill_parent"
  android:textSize="10px"
  android:text="Skew-Y: 0"
  />
  android:id="@+id/skewy"
  android:layout_height="wrap_content"
  android:layout_width="fill_parent"
  android:max="200"
  android:progress="100"
  />


  android:id="@+id/imageview"
  android:layout_gravity="center"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:scaleType="center"
  />

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 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(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];
  }};
}