拍摄照片与使用的UIImagePickerController

Question

特定分辨率下我想借的A4纸件的照片写上。重要的是，我希望文字是可读的，但我不希望与像2592x1936像素或3264X2448像素分辨率的图像，因为这将是太大了。此外，我认为拍摄后缩放照片需要额外的时间，所以我想避免这一点。

我们可以在下面的质量之间选择：

UIImagePickerControllerQualityTypeHigh = 0 
UIImagePickerControllerQualityTypeMedium   = 1 default value 
UIImagePickerControllerQualityTypeLow   = 2 
UIImagePickerControllerQualityType640x480   = 3, 
UIImagePickerControllerQualityTypeIFrame1280x720 = 4, 
UIImagePickerControllerQualityTypeIFrame960x540 = 5 

如果我们使用的AVFoundation，我们可以从this nice table选择分辨率（下标题“拍摄静态图像”）。

但是有没有类似的表为UIImagePickerController，例如说，UIImagePickerControllerQualityTypeHigh等于1920 x 1080在iPhone 3gs？

Answer 1

UIImagepickerController quality用于视频记录（在属性的UIImagePickerController“视频质量”使用）。

我想，如果你想指定确切的照片分辨率应该是什么，你应该使用AV Foundation框架，而不是的UIImagePickerController。或者如你所说，之后转换图片。

调整其大小之后（发现here）：

// ============================================================== 
// resizedImage 
// ============================================================== 
// Return a scaled down copy of the image. 

UIImage* resizedImage(UIImage *inImage, CGRect thumbRect) 
{ 
    CGImageRef   imageRef = [inImage CGImage]; 
    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef); 

    // There's a wierdness with kCGImageAlphaNone and CGBitmapContextCreate 
    // see Supported Pixel Formats in the Quartz 2D Programming Guide 
    // Creating a Bitmap Graphics Context section 
    // only RGB 8 bit images with alpha of kCGImageAlphaNoneSkipFirst, kCGImageAlphaNoneSkipLast, kCGImageAlphaPremultipliedFirst, 
    // and kCGImageAlphaPremultipliedLast, with a few other oddball image kinds are supported 
    // The images on input here are likely to be png or jpeg files 
    if (alphaInfo == kCGImageAlphaNone) 
     alphaInfo = kCGImageAlphaNoneSkipLast; 

    // Build a bitmap context that's the size of the thumbRect 
    CGContextRef bitmap = CGBitmapContextCreate(
       NULL, 
       thumbRect.size.width,  // width 
       thumbRect.size.height,  // height 
       CGImageGetBitsPerComponent(imageRef), // really needs to always be 8 
       4 * thumbRect.size.width, // rowbytes 
       CGImageGetColorSpace(imageRef), 
       alphaInfo 
     ); 

    // Draw into the context, this scales the image 
    CGContextDrawImage(bitmap, thumbRect, imageRef); 

    // Get an image from the context and a UIImage 
    CGImageRef ref = CGBitmapContextCreateImage(bitmap); 
    UIImage* result = [UIImage imageWithCGImage:ref]; 

    CGContextRelease(bitmap); // ok if NULL 
    CGImageRelease(ref); 

    return result; 
} 

希望这有助于！

Answer 2

一句话：没有。

没有“类似的表格”，因为您误解了UIImagePickerController如何使用UIImagePickerControllerQualityTypeHigh。

如果您使用UIImagePickerController拍摄静态图像，您可以使用iPod touch或iPad 2的1 MP从iPhone 4s到iPhone 4s到< 1 MP的任何地方以默认设备（即最高质量）获取它们。

随着AVFoundation，但是，你有选择，感谢你提到的会议预设。

但与这些AVFoundation会话预设不同，UIImagePickerControllerUIImagePickerControllerQualityType选项仅适用于运动视频，而不适用于静态图像捕获。

因此，您可以选择使用AVFoundation来控制捕捉大小，或在保存全尺寸图像之前重新调整大小;但是UIImagePickerController不能做你想做的，恐怕。

Answer 3

Thermometer's answer的问题在于它与图像方向有关。

我发现this solution，解决了定位问题，并且具有更快的性能：

- (UIImage *)scaleAndRotateImage:(UIImage *)image { 
    int kMaxResolution = 320; // Or whatever 

    CGImageRef imgRef = image.CGImage; 

    CGFloat width = CGImageGetWidth(imgRef); 
    CGFloat height = CGImageGetHeight(imgRef); 

    CGAffineTransform transform = CGAffineTransformIdentity; 
    CGRect bounds = CGRectMake(0, 0, width, height); 
    if (width > kMaxResolution || height > kMaxResolution) { 
     CGFloat ratio = width/height; 
     if (ratio > 1) { 
      bounds.size.width = kMaxResolution; 
      bounds.size.height = bounds.size.width/ratio; 
     } 
     else { 
      bounds.size.height = kMaxResolution; 
      bounds.size.width = bounds.size.height * ratio; 
     } 
    } 

    CGFloat scaleRatio = bounds.size.width/width; 
    CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); 
    CGFloat boundHeight; 
    UIImageOrientation orient = image.imageOrientation; 
    switch(orient) { 

     case UIImageOrientationUp: //EXIF = 1 
      transform = CGAffineTransformIdentity; 
      break; 

     case UIImageOrientationUpMirrored: //EXIF = 2 
      transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0); 
      transform = CGAffineTransformScale(transform, -1.0, 1.0); 
      break; 

     case UIImageOrientationDown: //EXIF = 3 
      transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height); 
      transform = CGAffineTransformRotate(transform, M_PI); 
      break; 

     case UIImageOrientationDownMirrored: //EXIF = 4 
      transform = CGAffineTransformMakeTranslation(0.0, imageSize.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(imageSize.height, imageSize.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, imageSize.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(imageSize.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; 
} 

Answer 4

为了您的斯威夫特2。1项目，这是@ marcelosalloum代码翻译：

func scaleAndRotateImage(image: UIImage, kMaxResolution: CGFloat) -> UIImage { 
    var imageCopy: UIImage = image 
    if let imgRef: CGImageRef = image.CGImage { 

     let width = CGFloat(CGImageGetWidth(imgRef)) 
     let height = CGFloat(CGImageGetHeight(imgRef)) 

     var transform = CGAffineTransformIdentity 
     var bounds = CGRectMake(0, 0, width, height) 

     if width > kMaxResolution || height > kMaxResolution { 
      let ratio = width/height 
      if ratio > 1 { 
       bounds.size.width = kMaxResolution 
       bounds.size.height = bounds.size.width/ratio 
      } else { 
       bounds.size.height = kMaxResolution 
       bounds.size.width = bounds.size.height * ratio 
      } 
     } 

     let scaleRatio = bounds.size.width/width 
     let imageSize = CGSizeMake(width, height) 
     let boundHeight: CGFloat 
     let orient: UIImageOrientation = image.imageOrientation 
     switch orient { 
     case .Up: 
      transform = CGAffineTransformIdentity 

     case .UpMirrored: 
      transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0) 
      transform = CGAffineTransformScale(transform, -1.0, 1.0) 

     case .Down: 
      transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height) 
      transform = CGAffineTransformRotate(transform, CGFloat(M_PI)) 

     case .DownMirrored: //EXIF = 4 
      transform = CGAffineTransformMakeTranslation(0.0, imageSize.height); 
      transform = CGAffineTransformScale(transform, 1.0, -1.0); 

     case .LeftMirrored: //EXIF = 5 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width); 
      transform = CGAffineTransformScale(transform, -1.0, 1.0); 
      transform = CGAffineTransformRotate(transform, 3.0 * CGFloat(M_PI)/2.0); 

     case .Left: //EXIF = 6 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeTranslation(0.0, imageSize.width); 
      transform = CGAffineTransformRotate(transform, 3.0 * CGFloat(M_PI)/2.0); 

     case .RightMirrored: //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, CGFloat(M_PI)/2.0); 

     case .Right: //EXIF = 8 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0); 
      transform = CGAffineTransformRotate(transform, CGFloat(M_PI)/2.0); 
     } 
     UIGraphicsBeginImageContext(bounds.size) 

     if let context: CGContextRef = UIGraphicsGetCurrentContext() { 
      if orient == .Right || orient == .Left { 
       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) 
      imageCopy = UIGraphicsGetImageFromCurrentImageContext() 
      UIGraphicsEndImageContext() 
     } 
    } 
    return imageCopy 
} 

Answer 5

一个快速的3翻译marcelosalloum's answer：

private func scale(image originalImage: UIImage, toLessThan maxResolution: CGFloat) -> UIImage? { 
    guard let imageReference = originalImage.cgImage else { return nil } 

    let rotate90 = CGFloat.pi/2.0 // Radians 
    let rotate180 = CGFloat.pi // Radians 
    let rotate270 = 3.0*CGFloat.pi/2.0 // Radians 

    let originalWidth = CGFloat(imageReference.width) 
    let originalHeight = CGFloat(imageReference.height) 
    let originalOrientation = originalImage.imageOrientation 

    var newWidth = originalWidth 
    var newHeight = originalHeight 

    if originalWidth > maxResolution || originalHeight > maxResolution { 
     let aspectRatio: CGFloat = originalWidth/originalHeight 
     newWidth = aspectRatio > 1 ? maxResolution : maxResolution * aspectRatio 
     newHeight = aspectRatio > 1 ? maxResolution/aspectRatio : maxResolution 
    } 

    let scaleRatio: CGFloat = newWidth/originalWidth 
    var scale: CGAffineTransform = .init(scaleX: scaleRatio, y: -scaleRatio) 
    scale = scale.translatedBy(x: 0.0, y: -originalHeight) 

    var rotateAndMirror: CGAffineTransform 

    switch originalOrientation { 
    case .up: 
     rotateAndMirror = .identity 

    case .upMirrored: 
     rotateAndMirror = .init(translationX: originalWidth, y: 0.0) 
     rotateAndMirror = rotateAndMirror.scaledBy(x: -1.0, y: 1.0) 

    case .down: 
     rotateAndMirror = .init(translationX: originalWidth, y: originalHeight) 
     rotateAndMirror = rotateAndMirror.rotated(by: rotate180) 

    case .downMirrored: 
     rotateAndMirror = .init(translationX: 0.0, y: originalHeight) 
     rotateAndMirror = rotateAndMirror.scaledBy(x: 1.0, y: -1.0) 

    case .left: 
     (newWidth, newHeight) = (newHeight, newWidth) 
     rotateAndMirror = .init(translationX: 0.0, y: originalWidth) 
     rotateAndMirror = rotateAndMirror.rotated(by: rotate270) 
     scale = .init(scaleX: -scaleRatio, y: scaleRatio) 
     scale = scale.translatedBy(x: -originalHeight, y: 0.0) 

    case .leftMirrored: 
     (newWidth, newHeight) = (newHeight, newWidth) 
     rotateAndMirror = .init(translationX: originalHeight, y: originalWidth) 
     rotateAndMirror = rotateAndMirror.scaledBy(x: -1.0, y: 1.0) 
     rotateAndMirror = rotateAndMirror.rotated(by: rotate270) 

    case .right: 
     (newWidth, newHeight) = (newHeight, newWidth) 
     rotateAndMirror = .init(translationX: originalHeight, y: 0.0) 
     rotateAndMirror = rotateAndMirror.rotated(by: rotate90) 
     scale = .init(scaleX: -scaleRatio, y: scaleRatio) 
     scale = scale.translatedBy(x: -originalHeight, y: 0.0) 

    case .rightMirrored: 
     (newWidth, newHeight) = (newHeight, newWidth) 
     rotateAndMirror = .init(scaleX: -1.0, y: 1.0) 
     rotateAndMirror = rotateAndMirror.rotated(by: CGFloat.pi/2.0) 
    } 

    UIGraphicsBeginImageContext(CGSize(width: newWidth, height: newHeight)) 
    guard let context = UIGraphicsGetCurrentContext() else { return nil } 
    context.concatenate(scale) 
    context.concatenate(rotateAndMirror) 
    context.draw(imageReference, in: CGRect(x: 0, y: 0, width: originalWidth, height: originalHeight)) 
    let copy = UIGraphicsGetImageFromCurrentImageContext() 
    UIGraphicsEndImageContext() 

    return copy 
    }