如何在UWPC#中設定影像和PDF大小

我正在嘗試在我的專案中生成一個 pdf，我將 Image 轉換為 Pdf 和從 Layout 生成的 Image。生成的影像尺寸非常大，也沒有收到好的質量。請幫我解決這個問題。

我在程式中使用此代碼。

 RenderTargetBitmap renderTargetBitmapimg = new RenderTargetBitmap();

            var mainlayoutHeight = pageStackPanel.ActualHeight;
            var mainlayoutWidth = pageStackPanel.ActualWidth;
            int mlHeight = Convert.ToInt32(mainlayoutHeight);
            int mlWidth = Convert.ToInt32(mainlayoutWidth);


            
            await renderTargetBitmapimg.RenderAsync(pageStackPanel, mlWidth, mlHeight);
            
            ///SAVE IMAGE IN FOLDER 
            var pixelBufferimg = await renderTargetBitmapimg.GetPixelsAsync();
            var pixels = pixelBufferimg.ToArray();
            var displayInformation = DisplayInformation.GetForCurrentView();
            var storageFolder = await KnownFolders.GetFolderForUserAsync(null, KnownFolderId.PicturesLibrary);

            StorageFolder projectFolder = await storageFolder.CreateFolderAsync("TestImage", CreationCollisionOption.OpenIfExists);
            var file = await projectFolder.CreateFileAsync(jpgFilename, CreationCollisionOption.GenerateUniqueName);

            using (var stream = await file.OpenAsync(FileAccessMode.ReadWrite))
            {
                var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, stream);
                encoder.SetPixelData(BitmapPixelFormat.Bgra8,
                                     BitmapAlphaMode.Premultiplied,
                                    (uint)renderTargetBitmapimg.PixelWidth,
                                    (uint)renderTargetBitmapimg.PixelHeight,
                                    200, 200,
                                    pixels);

                await encoder.FlushAsync();
                StorageFile prescriptionJpgFile = await projectFolder.GetFileAsync(jpgFilename);
                await stream.FlushAsync();
                stream.Seek(0);
                stream.Dispose();
                renderTargetBitmapimg = null;

uj5u.com熱心網友回復：

答案是否定的，你不能設定生成的影像檔案的大小。但是您可以嘗試通過提供特定的寬度和高度來調整它的大小以減小其物理尺寸。您可以使用 BitmapEncoder 類對原始影像進行編碼，更改影像的BitmapInterpolationMode。代碼如下所示：

    //open file as stream
        using (IRandomAccessStream fileStream = await imagefile.OpenAsync(FileAccessMode.ReadWrite))
        {
            var decoder = await BitmapDecoder.CreateAsync(fileStream);

            var resizedStream = new InMemoryRandomAccessStream();

            BitmapEncoder encoder = await BitmapEncoder.CreateForTranscodingAsync(resizedStream, decoder);
            double widthRatio = (double)reqWidth / decoder.PixelWidth;
            double heightRatio = (double)reqHeight / decoder.PixelHeight;

            double scaleRatio = Math.Min(widthRatio, heightRatio);

            if (reqWidth == 0)
                scaleRatio = heightRatio;

            if (reqHeight == 0)
                scaleRatio = widthRatio;

            uint aspectHeight = (uint)Math.Floor(decoder.PixelHeight * scaleRatio);
            uint aspectWidth = (uint)Math.Floor(decoder.PixelWidth * scaleRatio);

            encoder.BitmapTransform.InterpolationMode = BitmapInterpolationMode.Linear;

            encoder.BitmapTransform.ScaledHeight = aspectHeight;
            encoder.BitmapTransform.ScaledWidth = aspectWidth;

            await encoder.FlushAsync();
            resizedStream.Seek(0);
            var outBuffer = new byte[resizedStream.Size];
            await resizedStream.ReadAsync(outBuffer.AsBuffer(), (uint)resizedStream.Size, InputStreamOptions.None);


            StorageFolder storageFolder = ApplicationData.Current.LocalFolder;
            Debug.WriteLine(storageFolder.Path);
            StorageFile sampleFile = await storageFolder.CreateFileAsync("testfile.pdf", CreationCollisionOption.ReplaceExisting);
            await FileIO.WriteBytesAsync(sampleFile, outBuffer);

        }

有關更多資訊，您可以查看此檔案：如何壓縮影像并更改其大小。

另一個建議是您可以只使用 UWP 列印 API 來生成 PDF 檔案。你可以看看 Windows Community Toolkit 的Print Helper。您可以選擇不列印，而是將其保存為 PDF 檔案。

標籤：C＃ xml uwp

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