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;
}