Question

我旋转图像然后在ImageView中显示它，问题是它旋转后，它会向上和向右移动。

我的旋转代码，在使用此方法旋转后，它已保存到文件系统中：

private Bitmap rotateImage( Bitmap original, int degrees )
{
        final int height = original.getHeight(), width = original.getWidth();

        Matrix matrix = new Matrix();
        matrix.setRotate( degrees, width / 2, height / 2 );
        RectF rectF = new RectF( 0, 0, width, height );
        matrix.mapRect( rectF );
        Bitmap rotatedImage = Bitmap.createBitmap( (int)rectF.width(), (int)rectF.height(), original.getConfig() );
        Canvas canvas = new Canvas( rotatedImage );
        canvas.drawBitmap( original, matrix, new Paint( Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG | Paint.FILTER_BITMAP_FLAG ) );

        return rotatedImage;
}

我的代码从文件系统加载已保存的图像：

private Bitmap loadImage( String imagePath, int maxHeight, int maxWidth )
{
BitmapFactory.Options fOptions = new BitmapFactory.Options();
int fHeight, fWidth, scale;

fOptions.inJustDecodeBounds = true;
BitmapFactory.decodeFile( imagePath, fOptions );
fHeight = fOptions.outHeight;
fWidth = fOptions.outWidth;
scale = Math.max( maxHeight > 0 ? fHeight / maxHeight : 0,
                      maxWidth > 0 ? fWidth / maxWidth : 0 );

fOptions.inJustDecodeBounds = false;
fOptions.inSampleSize = scale;
fOptions.inPurgeable = true;

return BitmapFactory.decodeFile( imagePath, fOptions );
}

ImageView xml：

<ImageView android:id="@+id/image"
           android:layout_height="wrap_content"
           android:layout_margin="10dp"
           android:layout_width="match_parent"
           android:scaleType="centerCrop" />

图像旋转得很好，但是当它显示时，它会从它应该的位置向右和向上偏移，然后由ImageView裁剪掉。任何人都可以看到导致它被抵消的原因吗？

Answer 1

问题是您的枢轴是根据原始图像尺寸计算的，原始图像尺寸可能不是最终图像的中心。

在绘制图像之前，我会像这样设置矩阵：

//center the source image
matrix.setTranslate(-width/2, -height/2);
//rotate the image
matrix.postRotate(degrees);
//now move it to the center of your final image
matrix.postTranslate(rotatedImage.getWidth()/2, rotatedImage.getHeight()/2);

//now draw the image
canvas.drawBitmap( original, matrix, new Paint( Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG | Paint.FILTER_BITMAP_FLAG ) );

Answer 2

这是因为图像相对于左上角旋转。旋转图像后，将其移至width/2和height/2

旋转位图偏离中心

2 个答案: