相机出照片是横着的
原因:用相机拍摄出来的照片含有EXIF信息,UIImage的imageOrientation属性指的就是EXIF中的orientation信息。
如果我们忽略orientation信息,而直接对照片进行像素处理或者drawInRect等操作,得到的结果是翻转或者旋转90之后的样子。这是因为我们执行像素处理或者drawInRect等操作之后,imageOrientaion信息被删除了,imageOrientaion被重设为0,造成照片内容和imageOrientaion不匹配。
所以,在对照片进行处理之前,先将照片旋转到正确的方向,并且返回的imageOrientaion为0。
代码实现:
+(UIImage )fixOrientation:(UIImage )aImage {
if (aImage.imageOrientation == UIImageOrientationUp)
return aImage;
CGAffineTransform transform = CGAffineTransformIdentity;
switch (aImage.imageOrientation) {
case UIImageOrientationDown:
case UIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
transform = CGAffineTransformRotate(transform, M_PI);
break;
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
transform = CGAffineTransformRotate(transform, M_PI_2);
break;
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
transform = CGAffineTransformRotate(transform, -M_PI_2);
break;
default:
break;
}
switch (aImage.imageOrientation) {
case UIImageOrientationUpMirrored:
case UIImageOrientationDownMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
case UIImageOrientationLeftMirrored:
case UIImageOrientationRightMirrored:
transform = CGAffineTransformTranslate(transform, aImage.size.height, 0);
transform = CGAffineTransformScale(transform, -1, 1);
break;
default:
break;
}
CGContextRef ctx = CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
CGImageGetBitsPerComponent(aImage.CGImage), 0,
CGImageGetColorSpace(aImage.CGImage),
CGImageGetBitmapInfo(aImage.CGImage));
CGContextConcatCTM(ctx, transform);
switch (aImage.imageOrientation) {
case UIImageOrientationLeft:
case UIImageOrientationLeftMirrored:
case UIImageOrientationRight:
case UIImageOrientationRightMirrored:
// Grr...
CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
break;
default:
CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
break;
}
CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
UIImage *img = [UIImage imageWithCGImage:cgimg];
CGContextRelease(ctx);
CGImageRelease(cgimg);
return img;
}
将image转90,180,270度的方法
原理:使用quartz2D来画图片,然后使用ctm变幻来实现旋转。
quartz2D的绘图左边和oc里面的绘图左边不一样,导致绘画出的图片是反转的。所以一上来得使它转正再进行进一步的旋转等
代码实现:
+ (UIImage *)image:(UIImage *)image rotation:(UIImageOrientation)orientation
{
long double rotate = 0.0;
CGRect rect;
float translateX = 0;
float translateY = 0;
float scaleX = 1.0;
float scaleY = 1.0;
switch (orientation) {
case UIImageOrientationLeft:
rotate = M_PI_2;
rect = CGRectMake(0, 0, image.size.height, image.size.width);
translateX = 0;
translateY = -rect.size.width;
scaleY = rect.size.width/rect.size.height;
scaleX = rect.size.height/rect.size.width;
break;
case UIImageOrientationRight:
rotate = 3 * M_PI_2;
rect = CGRectMake(0, 0, image.size.height, image.size.width);
translateX = -rect.size.height;
translateY = 0;
scaleY = rect.size.width/rect.size.height;
scaleX = rect.size.height/rect.size.width;
break;
case UIImageOrientationDown:
rotate = M_PI;
rect = CGRectMake(0, 0, image.size.width, image.size.height);
translateX = -rect.size.width;
translateY = -rect.size.height;
break;
default:
rotate = 0.0;
rect = CGRectMake(0, 0, image.size.width, image.size.height);
translateX = 0;
translateY = 0;
break;
}
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
//做CTM变换
CGContextTranslateCTM(context, 0.0, rect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextRotateCTM(context, rotate);
CGContextTranslateCTM(context, translateX, translateY);
CGContextScaleCTM(context, scaleX, scaleY);
//绘制图片
CGContextDrawImage(context, CGRectMake(0, 0, rect.size.width, rect.size.height), image.CGImage);
UIImage *newPic = UIGraphicsGetImageFromCurrentImageContext();
return newPic;
}
文章参考:
http://www.jianshu.com/p/6df4ecae0b28 http://blog.sina.com.cn/s/blog_6602ffbc0101ckx3.html