how to Rotate bitmap by canvas

Question

I have a bitmap from camera , after resize , it change to horizontal , I need to rotate 90 degree , but most of the sample are use Matrix to rotate , but when I new Matrix , it said matrix is deprecated , than I try to use CANVAS , following this , first time to use it , trying to figure it out , but can not rotate it , app crash , help please

code

  resizePhoto = BitmapFactory.decodeFile(imageLocation,bmOption);

//  R o t a t e    B i t m a p   90 degree

    Canvas canvas = new Canvas(resizePhoto);
    canvas.rotate(90);
    canvas.drawBitmap(resizePhoto , null ,null);

in `drawBitmap(resizePhoto , null ,null);` you are using null `Matrix` which causes the crash — pskink, Mar 04 '16 at 10:27
@Bhargav http://developer.android.com/intl/zh-tw/reference/android/opengl/Matrix.html — Awei Hsue, Mar 04 '16 at 10:28
we are talking about `android.graphics.Matrix`, not about `android.opengl.Matrix` — pskink, Mar 04 '16 at 10:30
@pskink Thanks , but I try to create a matrix by useing Matrix matrix = new Matrix() , it say matrix is deprecated, or i shouldn't do this? — Awei Hsue, Mar 04 '16 at 10:30
@pskink OH! you are right! !!!! thank you !!! can u post answer , than I can vote you ! sorry , I'm noob — Awei Hsue, Mar 04 '16 at 10:33
@pskink, Can you look at https://stackoverflow.com/questions/65435556/canvas-rotate-and-drawbitmap? — Gunaseelan, Dec 28 '20 at 07:20

score 1 · Answer 1 · answered Mar 04 '16 at 10:38

1

Matrix matrix = new Matrix();
matrix.setRotate(angle, imageCenterX, imageCenterY);
yourCanvas.drawBitmap(yourBitmap, matrix, null);

answered Mar 04 '16 at 10:38

Hazonko

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thank you! I'm noob , I confuse android.graphics.Matrix, not about android.opengl.Matrix – Awei Hsue Mar 04 '16 at 10:41
It happens. don't beat yourself up about it. we're all constantly learning! – Hazonko Mar 04 '16 at 10:42
Make sure you use a different bitmap for the Canvas than the one you draw with. That will cause your crash. – Simon Mar 04 '16 at 10:42
if the answer was sufficient, please accept it. Thanks. – Hazonko Mar 07 '16 at 10:09

score 0 · Answer 2 · answered Mar 04 '16 at 10:47

You might want to rotate using a matrix passed into Bitmap.createBitmap. It should be faster than using a Canvas.

Matrix matrix = new Matrix();
matrix.setRotate(angle);
Bitmap resizePhoto = BitmapFactory.decodeFile(imageLocation, bmOption);
Bitmap rotatedPhoto = Bitmap.createBitmap(resizePhoto, 0, 0, 
    resizePhoto.getWidth(), resizePhoto.getHeight(), matrix, true);
resizePhoto.recycle();

You might need to swap the getWidth() and getHeight() around for an exact 90 degree rotation. I forget.

how to Rotate bitmap by canvas

2 Answers2