Develop Reference

Rotate around alternate axis

I am struggling with bitmap rotations. I wish to rotate a graphic around an alternate axis but I can only ever get it to rotate around the center point no matter what I do, putting in postTranlate. preTranslate, set Translate in any order doesnt work I have also tried the postRotate(45,0,0) but it always rotates around the center.
Code below taken of internet what would I do to alter its rotation point, the code below uses the launcher icon which is square I am using a long thin graphic like an arrow.
// Rotate image to 45 degrees.
public void RotateImage(){
ImageView image;
Bitmap bMap;
Matrix matrix;
//Get ImageView from layout xml file
image = (ImageView) findViewById(R.id.imageView1);
//Decode Image using Bitmap factory.
bMap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
//Create object of new Matrix.
matrix = new Matrix();
//set image rotation value to 45 degrees in matrix.
matrix.postRotate(45);
//Create bitmap with new values.
Bitmap bMapRotate = Bitmap.createBitmap(bMap, 0, 0,
bMap.getWidth(), bMap.getHeight(), matrix, true);
//put rotated image in ImageView.
image.setImageBitmap(bMapRotate);
}
I have tried the code below but its still rotates around the center or at least appears too
public void RotateImage{
ImageView image;
Bitmap bMap;
Matrix matrix;
//Get ImageView from layout xml file
image = (ImageView) findViewById(R.id.imageView);
//Decode Image using Bitmap factory.
bMap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
//Create object of new Matrix.
matrix = new Matrix();
//set image rotation value to 45 degrees in matrix.
matrix.setTranslate(-100,-200);
matrix.postRotate(angle);
matrix.postTranslate(100,200);
//Create bitmap with new values.
Bitmap bMapRotate = Bitmap.createBitmap(bMap, 0, 0,
bMap.getWidth(), bMap.getHeight(), matrix, true);
//put rotated image in ImageView.
image.setImageBitmap(bMapRotate);
Thanks

If you want your Bitmap to rotate 45 degree around x axis with pivot (a,b), you can call matrix.rotate(45, a, b)

Perhaps you want to use the Camera class to rotate around X, Y or Z axis:
matrix = new Matrix();
Camera camera = new Camera();
camera.save();
camera.rotateX(45f);
camera.getMatrix(matrix);
camera.restore();

The way I understand your question is that you want to rotate the image around some point, say (x, y). Conceptually you need to perform the following transformations on the image:
Translate by (-x, -y)
Rotate by 45 degrees
Translate by (x, y)

You can use this method to rotate an object from center create this method in sprite class
public void paintFromCenter(float angle, Canvas c) {
Bitmap b = sprite;
Bitmap h = b;
// Canvas canvas = new Canvas(a);
Matrix matrix = new Matrix();
matrix.postRotate(angle, h.getWidth() / 2, h.getHeight());
matrix.postTranslate(getX(), getY());
// canvas.drawBitmap(bitmap, matrix, new Paint());
Bitmap bmp2 = Bitmap.createBitmap(h, 0, 0, frameWidth, frameHeight,
matrix, true);
c.drawBitmap(h, matrix, null);
// g.getCanvas().drawBitmap(bmp2, getX(), getY(), null);
}
Now in onTouchEvent()
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_MOVE) {
evX = (int) event.getX();
evY = (int) event.getY();
int initX = objectSprite.getX();
int inity = objectSprite.getY();
if ((evX > objectSprite.getX()
&& evX < objectSprite.getX() + objectSprite.getWidth()
&& evY > objectSprite.getY() && evY < objectSprite.getY()
+ objectSprite.getHeight())) {
if (angle < 90) {
angle += 5;
} else if (angle < -180)
angle -= 5;
}
}
return true;
}
in draw() method paint the image/object
private void draw(Canvas canvas) {
objectSprite.paintFromCenter(angle, canvas);
}
try it

Set ImageView orientation directly in Android?

I understand that I can rotate an ImageView in Android by
matrix.postRotate(finalOrientation - initOrientation, width, height);
But I want to set it as finalOrientation directly instead of rotating it by the difference, finalOrientation - initOrientation.
So I am expecting something like:
matrix.setOrientation(finalOrientation);
How can I do that?

Perfect! thanks #Bette Devine!
I made a function just for convenience.
public Bitmap rotateBmp(Bitmap bmp){
Matrix matrix = new Matrix();
//set image rotation value to 90 degrees in matrix.
matrix.postRotate(90);
//supply the original width and height, if you don't want to change the height and width of bitmap.
bmp = Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(),bmp.getHeight(), matrix, true);
return bmp;
}
I had to do this with a downsized image. I got a "java.lang.OutOfMemoryError" when I tried to do this with a full size image. : (

Matrix matrix = new Matrix();
//set image rotation value to 90 degrees in matrix.
matrix.postRotate(90);
//supply the original width and height, if you don't want to change the height and width of bitmap.
Bitmap bMapRotate = Bitmap.createBitmap(bMap, 0, 0, newWidth, newHeight, matrix, true);

Please refer the following link:
http://docs.xamarin.com/guides/android/application_fundamentals/handling_rotation/

Android: image rotation not desire to resize

I have a code for rotate an ImageView, and good good.
The problem is that the size of image change in the rotate process and I desire that not happen.
The xml code of image
<ImageView
android:id="#+id/imgBallesta"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:src="#drawable/imgballesta"
android:contentDescription="#string/imageString"
/>
The code that creates the bitmap, I put this code in the declaration of class
Bitmap bMap = BitmapFactory.decodeResource(getResources(), R.drawable.imgObjectImage);
And the code for rotate the image, this code is inluded and onTouchEvent
Matrix mat = new Matrix();
matrix.postRotate((float) (angle*180/Math.PI), image.getWidth(),image.getHeight());
Bitmap bMapRotate = Bitmap.createBitmap(bMap, 0, 0, bMap.getWidth(), bMap.getHeight(), matrix, true);
image.setImageBitmap(bMapRotate);
Thanks for the help, and for read my question

Try with my method for rotate picture :
public static Bitmap rotate(Bitmap src, float degree) {
// create new matrix
Matrix matrix = new Matrix();
// setup rotation degree
matrix.postRotate(degree);
// return new bitmap rotated using matrix
return Bitmap.createBitmap(src, 0, 0, src.getWidth(), src.getHeight(), matrix, true);
}
Good luck!!

I found a posoble solution to my problem. First I modify the size and height of my image and create the respective image for all drawable folders.
Then I use the next code for to animate the image.
Matrix matrix=new Matrix();
img.setScaleType(ScaleType.MATRIX); //required
matrix.postRotate((float) (a*180/Math.PI) , img.getWidth()/2, img.getHeight()/2);
img.setImageMatrix(matrix);
Thanks for response and read this question.

How to translate and rotate in bitmap in android?

I am trying to translate and rotate a bitmap in android ImageView. But I can't get the result. Any pointers will be helpful.
int width = mb.getWidth();
int height = mb.getHeight();
// create a matrix for the manipulation
Matrix matrix = new Matrix();
matrix.preTranslate(width/2, height/2)
matrix.postRotate(angle);
Bitmap resizedBitmap = Bitmap.createBitmap(mb, 0, 0,
width, height, matrix, true);
imageview.setImageBitmap(resizedBitmap);

Android rotate bitmap 90 degrees results in squashed image. Need a true rotate between portrait and landscape

I am trying to rotate a bitmap image 90 degrees to change it from a landscape format to a portrait format. Example:
[a, b, c, d]
[e, f, g, h]
[i, j, k, l]
rotated 90 degree clockwise becomes
[i,e,a]
[j,f,b]
[k,g,c]
[l,h,d]
Using the code below (from an online example) the image is rotated 90 degrees but retains the landscape aspect ratio so you end up with a vertically squashed image. Am I doing something wrong? Is there another method I need to use? I am also willing to rotate the jpeg file that I'm using to create the bitmap if that is easier.
// create a matrix for the manipulation
Matrix matrix = new Matrix();
// resize the bit map
matrix.postScale(scaleWidth, scaleHeight);
// rotate the Bitmap
matrix.postRotate(90);
// recreate the new Bitmap
Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOriginal, 0, 0, widthOriginal, heightOriginal, matrix, true);

This is all you need to rotate the image:
Matrix matrix = new Matrix();
matrix.postRotate(90);
rotated = Bitmap.createBitmap(original, 0, 0,
original.getWidth(), original.getHeight(),
matrix, true);
In your code sample, you included a call to postScale. Could that be the reason your image is being stretched? Perhaps take that one out and do some more testing.

Here's how you would rotate it properly (this insures proper rotation of the image)
public static Bitmap rotate(Bitmap b, int degrees) {
if (degrees != 0 && b != null) {
Matrix m = new Matrix();
m.setRotate(degrees, (float) b.getWidth() / 2, (float) b.getHeight() / 2);
try {
Bitmap b2 = Bitmap.createBitmap(
b, 0, 0, b.getWidth(), b.getHeight(), m, true);
if (b != b2) {
b.recycle();
b = b2;
}
} catch (OutOfMemoryError ex) {
throw ex;
}
}
return b;
}

This code worked great for me:
Matrix matrix = new Matrix();
matrix.setRotate(90, 0, 0);
matrix.postTranslate(original.getHeight(), 0);
rotatedBitmap = Bitmap.createBitmap(newWidth, newHeight, original.getConfig());
Canvas tmpCanvas = new Canvas(rotatedBitmap);
tmpCanvas.drawBitmap(original, matrix, null);
tmpCanvas.setBitmap(null);

check the canvas size where you draw the bitmap, maybe your canvas is still landscape, so only the square part of the rotated bitmap could be seen.