Android How to rotate a bitmap on a center point

Question

I ve been looking for over a day for a solution to this problem but nothing helps  even the answers here  Documentation doesn t explain anything too   I am simply trying to get a rotation in the direction of another object  The problem is that the bitmap is not rotated around a fixed point  but rather around the bitmaps  0 0    Here is the code I am having troubles with     Matrix mtx   new Matrix      mtx reset      mtx preTranslate -centerX  -centerY     mtx setRotate  float direction  -centerX  -centerY     mtx postTranslate pivotX  pivotY     Bitmap rotatedBMP   Bitmap createBitmap bitmap  0  0  spriteWidth  spriteHeight  mtx  true     this bitmap   rotatedBMP    The weird part is  it doesn t matter how I change the values within pre postTranslate   and the float arguments in setRotation    Can someone please help and push me in the right direction

User · Answer

You can use something like following   Matrix matrix   new Matrix    matrix setRotate mRotation source getWidth   2 source getHeight   2   RectF rectF   new RectF 0  0  source getWidth    source getHeight     matrix mapRect rectF   Bitmap targetBitmap   Bitmap createBitmap rectF width    rectF height    config   Canvas canvas   new Canvas targetBitmap   canvas drawBitmap source  matrix  new Paint

User · Answer

Edited  optimized code     public static Bitmap RotateBitmap Bitmap source  float angle          Matrix matrix   new Matrix          matrix postRotate angle         return Bitmap createBitmap source  0  0  source getWidth    source getHeight    matrix  true       To get Bitmap from resources   Bitmap source   BitmapFactory decodeResource this getResources    R drawable your img

User · Answer

matrix reset    matrix setTranslate  anchor x  anchor y    matrix postRotate  float  rotation   0 0   matrix postTranslate positionOfAnchor x  positionOfAnchor x   c drawBitmap bitmap  matrix  null

User · Answer

I used this configurations and still have the problem of pixelization    Bitmap bmpOriginal   BitmapFactory decodeResource this getResources    R drawable map pin           Bitmap targetBitmap   Bitmap createBitmap  bmpOriginal getWidth                      bmpOriginal getHeight                      Bitmap Config ARGB 8888           Paint p   new Paint            p setAntiAlias true            Matrix matrix   new Matrix                   matrix setRotate  float  lock getDirection    float   bmpOriginal getWidth   2                    float  bmpOriginal getHeight   2             RectF rectF   new RectF 0  0  bmpOriginal getWidth    bmpOriginal getHeight             matrix mapRect rectF            targetBitmap   Bitmap createBitmap  int rectF width     int rectF height    Bitmap Config ARGB 8888             Canvas tempCanvas   new Canvas targetBitmap            tempCanvas drawBitmap bmpOriginal  matrix  p

User · Answer

I hope the following sequence of code will help you   Bitmap targetBitmap   Bitmap createBitmap targetWidth  targetHeight  config   Canvas canvas   new Canvas targetBitmap   Matrix matrix   new Matrix    matrix setRotate mRotation source getWidth   2 source getHeight   2   canvas drawBitmap source  matrix  new Paint       If you check the following method from  frameworks base graphics java android graphics Bitmap java  public static Bitmap createBitmap Bitmap source  int x  int y  int width  int height          Matrix m  boolean filter    this would explain what it does with rotation and translate

User · Answer

You can also rotate the ImageView using a RotateAnimation   RotateAnimation rotateAnimation   new RotateAnimation from  to  Animation RELATIVE TO SELF  0 5f  Animation RELATIVE TO SELF                  0 5f   rotateAnimation setInterpolator new LinearInterpolator     rotateAnimation setDuration ANIMATION DURATION   rotateAnimation setFillAfter true    imageView startAnimation rotateAnimation

User · Answer

I came back to this problem now that we are finalizing the game and I just thought to post what worked for me   This is the method for rotating the Matrix   this matrix reset    this matrix setTranslate this floatXpos  this floatYpos   this matrix postRotate  float this direction  this getCenterX    this getCenterY         this getCenterX   is basically the bitmaps X position   the bitmaps width   2   And the method for Drawing the bitmap  called via a RenderManager Class    canvas drawBitmap this bitmap  this matrix  null    So it is prettey straight forward but I find it abit strange that I couldn t get it to work by setRotate followed by postTranslate  Maybe some knows why this doesn t work  Now all the bitmaps rotate properly but it is not without some minor decrease in bitmap quality     Anyways  thanks for your help

User · Answer

Look at the sample from Google called Lunar Lander  the ship image there is rotated dynamically   Lunar Lander code sample

[android] Android: How to rotate a bitmap on a center point

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