UIImage的轉動偏移

Question

我有以下代碼

- (void)ComputeRotationWithRadians:(CGFloat)rad { 
    CGFloat width = exportImage.size.width; 
    CGFloat height = exportImage.size.height; 
    UIGraphicsBeginImageContext(CGSizeMake(width, height)); 
    CGContextRef ctxt = UIGraphicsGetCurrentContext(); 
    CGContextScaleCTM(ctxt, 1.0, -1.0); 
    CGContextTranslateCTM(ctxt, 0.0, -exportImage.size.height); 
    CGContextRotateCTM(ctxt, rad); 
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), exportImage.CGImage); 
    exportImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    [imageView setImage:exportImage]; 
} 

的問題是發生了旋轉圍繞左下角，當它已經圍繞中心計算。無論如何要改變這個？

Answer 1

您的代碼在旋轉之前先轉換矩陣。嘗試翻轉電話CGContextConcatCTM和CGContextTranslateCTM，讓您先旋轉。或者你正在尋找別的東西？