Xamarin.iOS 以 72 dpi

问题描述

photoOutput = new AVCapturePhotoOutput();
if (CaptureSession.CanAddOutput(photoOutput))
{
        CaptureSession.AddOutput(photoOutput);
        photoOutput.IsHighResolutionCaptureEnabled = true;
}

拍照按钮：

void TakePhoto()
{
        AVCapturePhotoSettings settings = GetCurrentPhotoSettings();
        photoOutput.CapturePhoto(settings,this);
}

AVCapturePhotoSettings GetCurrentPhotoSettings()
{
        AVCapturePhotoSettings photoSettings = AVCapturePhotoSettings.Create();

        var previewPixelType = photoSettings.AvailablePreviewPhotoPixelFormatTypes.First();

        var keys = new[]
        {
                new Nsstring(CVPixelBuffer.PixelFormatTypeKey),new Nsstring(CVPixelBuffer.WidthKey),new Nsstring(CVPixelBuffer.HeightKey),};

        var objects = new NSObject[]
        {
                previewPixelType,new NSNumber(160),new NSNumber(160)
        };

        var dictionary = new NSDictionary<Nsstring,NSObject>(keys,objects);
        photoSettings.PreviewPhotoFormat = dictionary;

        photoSettings.IsHighResolutionPhotoEnabled = true;
        return photoSettings;
}

[Export("captureOutput:didFinishProcessingPhotoSampleBuffer:previewPhotoSampleBuffer:resolvedSettings:bracketSettings:error:")]
void DidFinishProcessingPhoto(AVCapturePhotoOutput captureOutput,CMSampleBuffer photoSampleBuffer,CMSampleBuffer previewPhotoSampleBuffer,AVCaptureResolvedPhotoSettings resolvedSettings,AVCaptureBracketedStillimagesettings bracketSettings,NSError error)
    {
            if (photoSampleBuffer == null)
            {
                    Console.WriteLine($"Error occurred while capturing photo: {error}");
                    return;
            }

            NSData imageData = AVCapturePhotoOutput.GetJpegPhotoDataRepresentation(photoSampleBuffer,previewPhotoSampleBuffer);
    
            UIImage imageInfo = new UIImage(imageData);
                
            (Element as Cameraview).SetPhotoResult(imageInfo.AsJPEG().ToArray());
    }

作为执行此代码的结果，我获得了使用该函数保存的图像字节数组：

void SaveImageTest(string filename,byte[] arr)
    {
            UIImage img = new UIImage(NSData.FromArray(arr));
            var jpeg = img.AsJPEG();
                
            NSError error;
            jpeg.Save(filename,false,out error);
    }

将图像上传到服务器，我在图像详细信息中获得 96 DPI。 image details

我想创建 72 个 DPI 图像。，

我没有找到可理解的解决方案，也许 swift 无法创建此类图像，您可能知道用于图像转换的 Xamarin 库

解决方法

我们可以使用以下代码调整图像大小

/*
   sourceImage:the iamge that you download
   newSize the size you want ( for example 72*72)
*/
public UIImage ScalingImageToSize(UIImage sourceImage,CGSize newSize)
{


   UIGraphics.BeginImageContextWithOptions(newSize,false,UIScreen.MainScreen.Scale);
   sourceImage.Draw(new CGRect(0,newSize.Width,newSize.Height));

   UIImage newImage = UIGraphics.GetImageFromCurrentImageContext();

   UIGraphics.EndImageContext();

   return newImage;

  }