图片处理

1、将图片方向旋转为up方向

-(UIImage *)rotateImage:(UIImage *)aImage

{

    

    CGImageRef imgRef = aImage.CGImage;

    CGFloat width = CGImageGetWidth(imgRef);

    CGFloat height = CGImageGetHeight(imgRef);

    

    CGAffineTransform transform = CGAffineTransformIdentity;

    CGRect bounds = CGRectMake(0, 0, width, height);

    CGFloat scaleRatio = 1;

    CGFloat boundHeight;

    

    UIImageOrientation orient = aImage.imageOrientation;

    

    switch(orient){

        case UIImageOrientationUp: //EXIF = 1

            transform = CGAffineTransformIdentity;

            break;

            

        case UIImageOrientationUpMirrored: //EXIF = 2

            transform = CGAffineTransformMakeTranslation(width, 0.0);

            transform = CGAffineTransformScale(transform, -1.0, 1.0);

            break;

            

        case UIImageOrientationDown: //EXIF = 3

            transform = CGAffineTransformMakeTranslation(width, height);

            transform = CGAffineTransformRotate(transform, M_PI);

            break;

            

        case UIImageOrientationDownMirrored: //EXIF = 4

            transform = CGAffineTransformMakeTranslation(0.0, height);

            transform = CGAffineTransformScale(transform, 1.0, -1.0);

            break;

            

        case UIImageOrientationLeftMirrored: //EXIF = 5

            boundHeight = bounds.size.height;

            bounds.size.height = bounds.size.width;

            bounds.size.width = boundHeight;

            transform = CGAffineTransformMakeTranslation(height, width);

            transform = CGAffineTransformScale(transform, -1.0, 1.0);

            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);

            break;

            

        case UIImageOrientationLeft: //EXIF = 6

            boundHeight = bounds.size.height;

            bounds.size.height = bounds.size.width;

            bounds.size.width = boundHeight;

            transform = CGAffineTransformMakeTranslation(0.0, width);

            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);

            break;

            

        case UIImageOrientationRightMirrored: //EXIF = 7

            boundHeight = bounds.size.height;

            bounds.size.height = bounds.size.width;

            bounds.size.width = boundHeight;

            transform = CGAffineTransformMakeScale(-1.0, 1.0);

            transform = CGAffineTransformRotate(transform, M_PI / 2.0);

            break;

            

        case UIImageOrientationRight: //EXIF = 8

            boundHeight = bounds.size.height;

            bounds.size.height = bounds.size.width;

            bounds.size.width = boundHeight;

            transform = CGAffineTransformMakeTranslation(height, 0.0);

            transform = CGAffineTransformRotate(transform, M_PI / 2.0);

            break;

            

        default:

            

            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

    }

    UIGraphicsBeginImageContext(bounds.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    

    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {

        CGContextScaleCTM(context, -scaleRatio, scaleRatio);

        CGContextTranslateCTM(context, -height, 0);

    }

    else {

        CGContextScaleCTM(context, scaleRatio, -scaleRatio);

        CGContextTranslateCTM(context, 0, -height);

    }

    

    CGContextConcatCTM(context, transform);

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);

    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    

    return imageCopy;

}

 

2、图片缩略图

- (UIImage *) thumbnailImageForImage:(UIImage *) image {

    CGSize origImageSize = image.size;

    

    CGRect newRect = CGRectMake(0, 0, 270, 233);

    float ratio = MAX(newRect.size.width / origImageSize.width, newRect.size.height/origImageSize.height);

    

    UIGraphicsBeginImageContext(newRect.size);

    CGRect projectRect;

    projectRect.size.width = ratio * origImageSize.width;

    projectRect.size.height = ratio * origImageSize.height;

    projectRect.origin.x = (newRect.size.width - projectRect.size.width) * 0.5;

    projectRect.origin.y = (newRect.size.height - projectRect.size.height) * 0.5;

    

    [image drawInRect:projectRect];

    

    UIImage * small = UIGraphicsGetImageFromCurrentImageContext();

    return small;

}