在裁剪之前调整UIImage或CIImage的大小，拉伸图像？

好吧，我已经试过了我可以找到的所有例子，可悲的是，其中大部分都是从2008年到2009年，而iOS5似乎有很大的不同。我只是想调整大小和图像，以便短边是我指定的大小，并保持不变。在裁剪之前调整UIImage或CIImage的大小，拉伸图像？

我使用AVFoundation从相机抓取图像，我通过UIImage将其转换为CIImage，以便在转换回UIImage进行保存之前应用滤镜和小提琴。

- (void) startCamera { 

session = [[AVCaptureSession alloc] init]; 
session.sessionPreset = AVCaptureSessionPresetPhoto; 

AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session]; 
captureVideoPreviewLayer.frame = _cameraView.bounds; 
[_cameraView.layer addSublayer:captureVideoPreviewLayer]; 
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill; 

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; 
NSError *error = nil; 

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error]; 
if (!input) { 
    //no cam, handle error - need to put up a nice happy note here 
    NSLog(@"ERROR: %@", error); 
} 

[session addInput:input]; 

stillImage = [[AVCaptureStillImageOutput alloc] init]; 
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG , AVVideoCodecKey, nil]; 
[stillImage setOutputSettings:outputSettings]; 

[session addOutput:stillImage]; 
[session startRunning]; 
} 

- (IBAction) _cameraButtonPress:(id)sender { 

AVCaptureConnection *videoConnection = nil; 
for (AVCaptureConnection *connection in stillImage.connections) 
{ 
    for (AVCaptureInputPort *port in [connection inputPorts]) 
    { 
     if ([[port mediaType] isEqual:AVMediaTypeVideo]) 
     { 
      videoConnection = connection; 
      break; 
     } 
    } 
    if (videoConnection) { 
     break; 
    } 
} 

[stillImage captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageSampleBuffer, NSError *error) { 

    NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer]; 
    UIImage *startImage = [[UIImage alloc] initWithData:imageData]; 

    //resizing of image to take place before anything else 
    UIImage *image = [startImage imageScaledToFitSize:_exportSSize]; //resizes to the size given in the prefs 

    //change the context to render using cpu, so on app exit renders get completed 
    context = [CIContext contextWithOptions: 
       [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] 
              forKey:kCIContextUseSoftwareRenderer]]; 

    //set up the saving library 
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init]; 

    //create a new ciimage 
    CIImage *greyImage = [[CIImage alloc] initWithCGImage:[image CGImage]]; 

    //create a CIMonochrome filter 
    desaturate = [CIFilter filterWithName:@"CIColorMonochrome" keysAndValues:kCIInputImageKey, greyImage, @"inputIntensity", [NSNumber numberWithFloat:0.00], nil]; 

    //[crop setValue:ciImage forKey:@"inputImage"]; 
    //[crop setValue:[CIVector vectorWithX:0.0f Y:0.0f Z:_exportSize W:_exportSize] forKey:@"inputRectangle"]; 

    CIImage *croppedColourImage = [desaturate valueForKey:@"outputImage"]; 
    //convert it to a cgimage for saving 
    CGImageRef cropColourImage = [context createCGImage:croppedColourImage fromRect:[croppedColourImage extent]]; 

    //saving of the images   
    [library writeImageToSavedPhotosAlbum:cropColourImage metadata:[croppedColourImage properties] completionBlock:^(NSURL *assetURL, NSError *error){ 
    if (error) { 
     NSLog(@"ERROR in image save: %@", error); 
    } else 
    { 
     NSLog(@"SUCCESS in image save"); 
     //in here we'll put a nice animation or something 
     CGImageRelease(cropColourImage); 
    } 

    }]; 
}]; 
}

此代码是测试代码，所以会有各种各样的尝试，为此道歉。

我有使用马特Gemmell代码here

最接近但是，无论我怎么努力，总是绵延的图像。我想调整图像大小，然后将其裁剪为512像素平方。如果我只是做一个CICrop过滤器，它需要左上512像素，所以我失去了很多图像（抓取高分辨率的照片，因为后来我还想导出1800x1800图像）。我的想法是先调整图像大小，然后裁剪。但是无论我做什么，图像都会变得很紧张。

所以我的问题是，有没有适当的建议公认的方式来调整大小和图像在iOS5 +？

谢谢。

来源

2012-05-07 mrEmpty

我发现这样做的一种方式：UIGraphicsBeginImageContext（新尺寸）; [image drawInRect：CGRectMake（0,0，newSize.width，newSize.height）]; UIImage * newImage = UIGraphicsGetImageFromCurrentImageContext（）; UIGraphicsEndImageContext（）;这可能不是我应该的方式，但它现在工作。想知道为什么苹果没有让这个更容易！ :) – mrEmpty

我刚刚遇到了这个完全相同的问题，但您建议的模型似乎不适用于我。我在这里发布了这个问题http://stackoverflow.com/questions/10491080/uiimage-resizing-not-working-properly –

而且我在另一个线程中也提供了一个适用于我的解决方案（它可以在iOS 5中正常工作）：http://stackoverflow.com/questions/10491080/uiimage-resizing-not-working-properly/10491692#10491692 – Rob

我发现这样做的一种方式：

UIGraphicsBeginImageContext(newSize); 

[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)]; 

UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext(); 

UIGraphicsEndImageContext();

来源

2012-05-29 13:03:24 mrEmpty

在裁剪之前调整UIImage或CIImage的大小，拉伸图像？

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