iOS:使用叠加层裁剪从UIImagePickerController摄像头抓取的静止图像

Question

我是iOS的新手,过去一周在网上寻找教程,例如:处理Exif图像,调整图像大小以及StackOverflow上的更多随机问题,我一直在抨击iOS .从这些,我想,>=iOS 4.0从相机拍摄的所有图像都包含EXIF基于旋转的信息.

什么不起作用:在尝试不同的图像裁剪技术之后,我最终得到的是在一些随机角落处裁剪图像,并且所得到的图像似乎被放大:(当我使用png来自互联网的图像时(其中)包含EXIF数据),裁剪工作正常.通过随机角落,我的意思是 - 图像最终被裁剪在右上角/左上角并放大.

我想要实现的目标:
我正在尝试100 px从顶部和100 px底部裁剪图像.基本上,我使用两个覆盖条 - 顶部1个,底部1个 CGRect(0.0, 0.0, SCREEN_WIDTH, 100.0)[ 100.0 px顶部有一个高条]和另一个CGRect(0.0, SCREEN_HEIGHT - 100, SCREEN_WIDTH, 100.0)[ 100 px底部另一个高条].我需要在这两个条带之间获取图像:我假设图像的高度为:SCREEN_HEIGHT - 200.0.

显示带覆盖的摄像头的UIImagePickerController:

    //SCREEN_HEIGHT = 480 and SCREEN_WIDTH = 320
    UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];

    if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera] == NO) 
    {
        NSLog(@"Camera not available");
        return;
    }

    imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
    imagePicker.delegate = self;
    imagePicker.allowsEditing = NO;


    // Hide the controls
    imagePicker.showsCameraControls = NO;
    imagePicker.navigationBarHidden = YES;

    // Make camera view full screen
    imagePicker.wantsFullScreenLayout = YES;
    //imagePicker.cameraViewTransform = CGAffineTransformScale(imagePicker.cameraViewTransform, CAMERA_TRANSFORM_X, CAMERA_TRANSFORM_Y);


    //Overlay
    //OverlayView is a plain UIView with the CGRects mentioned in the question.
    OverlayView *overlay = [[OverlayView alloc] initWithFrame:CGRectMake(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT)]; 
    [overlay initOverlay:self];
    imagePicker.cameraOverlayView = overlay;
    [self presentModalViewController:imagePicker animated:YES];

代码根据EXIF imageOrientation属性旋转图像并裁剪它

- (UIImage *) cropImage: (UIImage *) originalImage 
{

    CGRect cropRect = CGRectMake(0, 100.0, SCREEN_WIDTH, SCREEN_HEIGHT - 100);

    CGRect transformedRect = [self TransformCGRectForUIImageOrientation:cropRect :originalImage.imageOrientation :originalImage.size];

    CGImageRef resultImageRef = CGImageCreateWithImageInRect(originalImage.CGImage, transformedRect);

    UIImage *newImage = [[[UIImage alloc] initWithCGImage:resultImageRef scale:1.0 orientation:originalImage.imageOrientation] autorelease];

    return newImage;
}

- (CGRect) TransformCGRectForUIImageOrientation: (CGRect) source: (UIImageOrientation) orientation: (CGSize) imageSize {

    switch (orientation) {
        case UIImageOrientationLeft: { // EXIF #8
            CGAffineTransform txTranslate = CGAffineTransformMakeTranslation(
                                                                             imageSize.height, 0.0);
            CGAffineTransform txCompound = CGAffineTransformRotate(txTranslate,
                                                                   M_PI_2);
            return CGRectApplyAffineTransform(source, txCompound);
        }
        case UIImageOrientationDown: { // EXIF #3
            CGAffineTransform txTranslate = CGAffineTransformMakeTranslation(
                                                                             imageSize.width, imageSize.height);
            CGAffineTransform txCompound = CGAffineTransformRotate(txTranslate,
                                                                   M_PI);
            return CGRectApplyAffineTransform(source, txCompound);
        }
        case UIImageOrientationRight: { // EXIF #6
            CGAffineTransform txTranslate = CGAffineTransformMakeTranslation(
                                                                             0.0, imageSize.width);
            CGAffineTransform txCompound = CGAffineTransformRotate(txTranslate,
                                                                   M_PI + M_PI_2);
            return CGRectApplyAffineTransform(source, txCompound);
        }
        case UIImageOrientationUp: // EXIF #1 - do nothing
        default: // EXIF 2,4,5,7 - ignore
            return source;
    }

该cropImage方法似乎适用于从互联网下载的图像(不包含任何方向信息).我的选项已经用完了.有人可以帮帮我吗？

谢谢阅读!

Answer 1

如果可以,使用Core Graphics跳过绘图图像会更容易:

- (UIImage *)cropImage:(UIImage *)oldImage {
    CGSize imageSize = oldImage.size
    UIGraphicsBeginImageContextWithOptions( CGSizeMake( imageSize.width,
                                                        imageSize.height - 200),
                                            NO,
                                            0.);
    [oldImage drawAtPoint:CGPointMake( 0, -100)
                blendMode:kCGBlendModeCopy
                    alpha:1.];
    UIImage *croppedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return croppedImage;
}