pdf生成颠倒

Question

我正在使用以下代码创建pdf

UIImage *CurImage=[UIImage imageWithContentsOfFile:[ImageArr objectAtIndex:i]];
UIView *ViewDraw=[[UIView alloc]initWithFrame:CGRectMake(0,10, pageSize, pageSize)];  
ViewDraw.backgroundColor=[UIColor clearColor];
CGContextBeginPage (pdfContext,nil);

//turn PDF upsidedown
CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformMakeTranslation(0,CurImage.size.height);
transform = CGAffineTransformScale(transform, 1.0, -1.0);

CGContextConcatCTM(pdfContext, transform);
int y = (pageSize - CurImage.size.height)/2;
int x = (pageSize - CurImage.size.width)/2;

[CurImage drawInRect:CGRectMake( (ViewDraw.frame.width - curImage.frame.width)/2, 24, size.width, curImage.frame.height)];

//        CGContextDrawImage(pdfContext, CGRectMake(x,-y, CurImage.size.width, CurImage.size.height), CurImage.CGImage);
CGContextEndPage (pdfContext);
CurImage=nil;

但它正在颠倒产生，即180度镜像。

这里有什么问题？