如何将位图旋转90度

There is a statement in android canvas.drawBitmap(visiblePage, 0, 0, paint);

android canvas.drawBitmap中有一个语句（visiblePage，0,0，paint）;

When I add canvas.rotate(90), there is no effect. But if I write

当我添加canvas.rotate（90）时，没有任何效果。但是如果我写的话

canvas.rotate(90)
canvas.drawBitmap(visiblePage, 0, 0, paint);

I get no bitmap drawn. So what am I not doing right?

我没有得到位图。那么我做得对不对？

7 个解决方案

#1

You can also try this one

你也可以试试这个

Matrix matrix = new Matrix();

matrix.postRotate(90);

Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmapOrg, width, height, true);

Bitmap rotatedBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);

Then you can use the rotated image to set in your imageview through

然后，您可以使用旋转的图像在imageview中设置

imageView.setImageBitmap(rotatedBitmap);

#2

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:

要从资源中获取位图：

Bitmap source = BitmapFactory.decodeResource(this.getResources(), R.drawable.your_img);

#3

Below is the code to rotate or re size your image in android

下面是在android中旋转或重新调整图像大小的代码

public class bitmaptest extends Activity {
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        LinearLayout linLayout = new LinearLayout(this);

        // load the origial BitMap (500 x 500 px)
        Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(),
               R.drawable.android);

        int width = bitmapOrg.width();
        int height = bitmapOrg.height();
        int newWidth = 200;
        int newHeight = 200;

        // calculate the scale - in this case = 0.4f
        float scaleWidth = ((float) newWidth) / width;
        float scaleHeight = ((float) newHeight) / height;

        // createa matrix for the manipulation
        Matrix matrix = new Matrix();
        // resize the bit map
        matrix.postScale(scaleWidth, scaleHeight);
        // rotate the Bitmap
        matrix.postRotate(45);

        // recreate the new Bitmap
        Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0,
                          width, height, matrix, true);

        // make a Drawable from Bitmap to allow to set the BitMap
        // to the ImageView, ImageButton or what ever
        BitmapDrawable bmd = new BitmapDrawable(resizedBitmap);

        ImageView imageView = new ImageView(this);

        // set the Drawable on the ImageView
        imageView.setImageDrawable(bmd);

        // center the Image
        imageView.setScaleType(ScaleType.CENTER);

        // add ImageView to the Layout
        linLayout.addView(imageView,
                new LinearLayout.LayoutParams(
                      LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT
                )
        );

        // set LinearLayout as ContentView
        setContentView(linLayout);
    }
}

You can also check this link for details : http://www.anddev.org/resize_and_rotate_image_-_example-t621.html

您还可以查看此链接以获取详细信息：http：//www.anddev.org/resize_and_rotate_image_-_example-t621.html

#4

Short extension for Kotlin

Kotlin短暂延期

fun Bitmap.rotate(degrees: Float): Bitmap {
    val matrix = Matrix().apply { postRotate(degrees) }
    return Bitmap.createBitmap(this, 0, 0, width, height, matrix, true)
}

And usage:

用法：

val rotatedBitmap = bitmap.rotate(90)

#5

By default the rotation point is the Canvas's (0,0) point, and my guess is that you may want to rotate it around the center. I did that:

默认情况下，旋转点是Canvas的（0,0）点，我的猜测是您可能希望围绕中心旋转它。我这样做了：

protected void renderImage(Canvas canvas)
{
    Rect dest,drawRect ;

    drawRect = new Rect(0,0, mImage.getWidth(), mImage.getHeight());
    dest = new Rect((int) (canvas.getWidth() / 2 - mImage.getWidth() * mImageResize / 2), // left
                    (int) (canvas.getHeight()/ 2 - mImage.getHeight()* mImageResize / 2), // top
                    (int) (canvas.getWidth() / 2 + mImage.getWidth() * mImageResize / 2), //right
                    (int) (canvas.getWidth() / 2 + mImage.getHeight()* mImageResize / 2));// bottom

    if(!mRotate) {
        canvas.drawBitmap(mImage, drawRect, dest, null);
    } else {
        canvas.save(Canvas.MATRIX_SAVE_FLAG); //Saving the canvas and later restoring it so only this image will be rotated.
        canvas.rotate(90,canvas.getWidth() / 2, canvas.getHeight()/ 2);
        canvas.drawBitmap(mImage, drawRect, dest, null);
        canvas.restore();
    }
}

#6

If you rotate bitmap, 90 180 270 360 is ok but for other degrees canvas will draw bitmap with different size.

如果你旋转位图，90 180 270 360是可以的，但对于其他度数画布将绘制不同大小的位图。

So,the best way is

所以，最好的方法是

canvas.rotate(degree,rotateCenterPoint.x,rotateCenterPoint.y);  
canvas.drawBitmap(...);
canvas.rotate(-degree,rotateCenterPoint.x,rotateCenterPoint.y);//rotate back

#7

In case your goal is to have a rotated image in an imageView or file you can use Exif to achieve that. The support library now offers that: https://android-developers.googleblog.com/2016/12/introducing-the-exifinterface-support-library.html

如果您的目标是在imageView或文件中使用旋转图像，则可以使用Exif来实现该目标。支持库现在提供：https：//android-developers.googleblog.com/2016/12/introducing-the-exifinterface-support-library.html

Below is its usage but to achieve your goal you have to check the library api documentation for that. I just wanted to give a hint that rotating the bitmap isn't always the best way.

以下是它的用法，但要实现您的目标，您必须检查库api文档。我只想提示旋转位图并不总是最好的方法。

Uri uri; // the URI you've received from the other app
InputStream in;
try {
  in = getContentResolver().openInputStream(uri);
  ExifInterface exifInterface = new ExifInterface(in);
  // Now you can extract any Exif tag you want
  // Assuming the image is a JPEG or supported raw format
} catch (IOException e) {
  // Handle any errors
} finally {
  if (in != null) {
    try {
      in.close();
    } catch (IOException ignored) {}
  }
}

int rotation = 0;
int orientation = exifInterface.getAttributeInt(
    ExifInterface.TAG_ORIENTATION,
    ExifInterface.ORIENTATION_NORMAL);
switch (orientation) {
  case ExifInterface.ORIENTATION_ROTATE_90:
    rotation = 90;
    break;
  case ExifInterface.ORIENTATION_ROTATE_180:
    rotation = 180;
    break;
  case ExifInterface.ORIENTATION_ROTATE_270:
    rotation = 270;
    break;
}

dependency

依赖

compile "com.android.support:exifinterface:25.1.0"

编译“com.android.support:exifinterface:25.1.0”