xamarin.forms – Xamarin表单 – 调整相机图片大小

有人帮助我使用xamarin表格实验室相机获取此代码：

picker = DependencyService.Get<IMediaPicker> ();  
                task = picker.TakePhotoAsync (new CameraMediaStorageOptions {
                    DefaultCamera = CameraDevice.Rear,MaxPixelDimension = 800,});

                img.BackgroundColor = Color.Gray;

                Device.StartTimer (TimeSpan.FromMilliseconds (250),() => {
                    if (task != null) {
                        if (task.Status == TaskStatus.RanToCompletion) {
                            Device.BeginInvokeOnMainThread (async () => {
                                //img.Source = ImageSource.FromStream (() => task.Result.Source);
                                var fileAccess = Resolver.Resolve<IFileAccess> ();
                                string imageName = "img_user_" + User.CurrentUser().id + "_" + DateTime.Now.ToString ("yy_MM_dd_HH_mm_ss") + ".jpg";
                                fileName = imageName;

                                fileAccess.WriteStream (imageName,task.Result.Source);
                                fileLocation = fileAccess.FullPath(imageName);

                                FileStream fileStream = new FileStream(fileAccess.FullPath(imageName),FileMode.Open,System.IO.FileAccess.Read);
                                imageUrl = (string)test[0]["url"];
                                img.Source = imageUrl;
                            }); 
                        }

                            return  task.Status != TaskStatus.Canceled
                            && task.Status != TaskStatus.Faulted
                            && task.Status != TaskStatus.RanToCompletion;
                    }
                    return true;
                });

它可以保存图像,但手机拍照的实际尺寸很大,有没有办法调整尺寸.

解决方法

更新：原始答案没有用,请参阅下面的更新答案.问题是PCL库非常慢并且消耗了太多内存.

原始答案(不要使用)：

我发现了一个图像I / O库,ImageTools-PCL,它是我forked on github并修剪了在Xamarin中无法编译的内容,将修改保持在最低限度并且结果似乎有效.

要使用它,请下载链接的存储库,使用Xamarin进行编译,并将Build文件夹中的DLL添加到Forms项目中.

要调整图像大小,您可以执行此操作(应该适合您的问题的上下文)

var decoder = new   ImageTools.IO.Jpeg.JpegDecoder ();
ImageTools.ExtendedImage inImage = new ImageTools.ExtendedImage ();

decoder.Decode (inImage,task.Result.Source); 

var outImage = ImageTools.ExtendedImage.Resize (inImage,1024,new ImageTools.Filtering.BilinearResizer ());

var encoder = new ImageTools.IO.Jpeg.JpegEncoder ();
encoder.Encode (outImage,fileAccess.CreateStream (imageName));


ImageSource imgSource = ImageSource.FromFile (fileAccess.FullPath (imageName));

更新的答案：

从nuget获取Xamarin.XLabs,learn about using Resolver,使用Resize方法创建一个IImageService接口.

iOS的实现：

public class ImageServiceIOS: IImageService{
   public void ResizeImage(string sourceFile,string targetFile,float maxWidth,float maxHeight)
    {  
        if (File.Exists(sourceFile) && !File.Exists(targetFile))
        {
            using (UIImage sourceImage = UIImage.FromFile(sourceFile))
            {  
                var sourceSize = sourceImage.Size;
                var maxResizeFactor = Math.Min(maxWidth / sourceSize.Width,maxHeight / sourceSize.Height);

                if (!Directory.Exists(Path.GetDirectoryName(targetFile)))
                    Directory.CreateDirectory(Path.GetDirectoryName(targetFile));

                if (maxResizeFactor > 0.9)
                {
                    File.Copy(sourceFile,targetFile);
                }
                else
                { 
                    var width = maxResizeFactor * sourceSize.Width;
                    var height = maxResizeFactor * sourceSize.Height;

                    UIGraphics.BeginImageContextWithOptions(new CGSize((float)width,(float)height),true,1.0f);  
                    //  UIGraphics.GetCurrentContext().RotateCTM(90 / Math.PI);
                    sourceImage.Draw(new CGRect(0,(float)width,(float)height)); 

                    var resultImage = UIGraphics.GetImageFromCurrentImageContext();
                    UIGraphics.EndImageContext();


                    if (targetFile.ToLower().EndsWith("png"))
                        resultImage.AsPNG().Save(targetFile,true);
                    else
                        resultImage.AsJPEG().Save(targetFile,true);
                }
            }
        }
    }
}

Android服务的实施：

public class ImageServiceDroid: IImageService{
public void ResizeImage(string sourceFile,float maxHeight)
{ 
    if (!File.Exists(targetFile) && File.Exists(sourceFile))
    {   
        // First decode with inJustDecodeBounds=true to check dimensions
        var options = new BitmapFactory.Options()
        {
            InJustDecodeBounds = false,InPurgeable = true,};

        using (var image = BitmapFactory.DecodeFile(sourceFile,options))
        {  
            if (image != null)
            {
                var sourceSize = new Size((int)image.GetBitmapInfo().Height,(int)image.GetBitmapInfo().Width);

                var maxResizeFactor = Math.Min(maxWidth / sourceSize.Width,maxHeight / sourceSize.Height);

                string targetDir = System.IO.Path.GetDirectoryName(targetFile);
                if (!Directory.Exists(targetDir))
                    Directory.CreateDirectory(targetDir);

                if (maxResizeFactor > 0.9)
                { 
                    File.Copy(sourceFile,targetFile);
                }
                else
                { 
                    var width = (int)(maxResizeFactor * sourceSize.Width);
                    var height = (int)(maxResizeFactor * sourceSize.Height);

                    using (var bitmapScaled = Bitmap.CreateScaledBitmap(image,height,width,true))
                    {
                        using (Stream outStream = File.Create(targetFile))
                        {
                            if (targetFile.ToLower().EndsWith("png"))
                                bitmapScaled.Compress(Bitmap.CompressFormat.Png,100,outStream);
                            else
                                bitmapScaled.Compress(Bitmap.CompressFormat.Jpeg,95,outStream);
                        }
                        bitmapScaled.Recycle();
                    }
                }

                image.Recycle();
            }
            else
                Log.E("Image scaling Failed: " + sourceFile);
        }
    }
}
}

原文链接：https://www.f2er.com/html/225341.html

xamarin.forms – Xamarin表单 – 调整相机图片大小

解决方法

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