Generate document pages preview Leave feedback
GroupDocs.Merger provides PreviewOptions class to specify different options to manage preview of document pages.
Here are the steps to generate document preview with GroupDocs.Merger:
- Create new instance of Merger class and pass source document path as a constructor parameter.
- Instantiate the PreviewOptions object with:
- delegate for each page stream creation (see event handler CreatePageStream);
- image preview format - PNG / JPG / BMP;
- page numbers to process;
- custom size of preview images (if needed). NoteStream that were created by CreatePageStream delegate will be disposed automatically once after generation of preview image. If you need to implement custom image preview stream disposing you have to pass additional argument ReleasePageStream to clean up resources.
- Call GeneratePreview method of Merger class instance and pass PreviewOptions to it.
GroupDocs.Merger expects CreatePageStream delegate to obtain each page stream for image preview generation process
private static Stream CreatePageStream(int pageNumber)
{
string imageFilePath = Path.Combine("GeneratePreviewFolder", "image-" + pageNumber.ToString() + ".jpg");
var folder = Path.GetDirectoryName(imageFilePath);
if(!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
return new System.IO.FileStream(imageFilePath, FileMode.Create);
}
private static void ReleasePageStream(int pageNumber, Stream pageStream)
{
pageStream.Dispose();
string imageFilePath = Path.Combine("GeneratePreviewFolder", "image-" + pageNumber.ToString() + ".jpg");
Console.WriteLine("Image file {0} is ready for preview", imageFilePath);
}
public static void GetPreview()
{
string filePath = @"c:\sample.xlsx";
using (Merger merger = new Merger(filePath))
{
IPreviewOptions previewOption = new PreviewOptions(CreatePageStream, PreviewMode.JPEG);
merger.GeneratePreview(previewOption);
}
}
private static Stream CreatePageStream(int pageNumber)
{
string imageFilePath = Path.Combine("GeneratePreviewFolder", "image-" + pageNumber.ToString() + ".jpg");
var folder = Path.GetDirectoryName(imageFilePath);
if(!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
return new System.IO.FileStream(imageFilePath, FileMode.Create);
}
public static void GetPreview()
{
string filePath = @"c:\sample.xlsx";
using (Merger merger = new Merger(filePath))
{
IPreviewOptions previewOption = new PreviewOptions(CreatePageStream, ReleasePageStream, PreviewMode.JPEG);
merger.GeneratePreview(previewOption);
}
}
private static Stream CreatePageStream(int pageNumber)
{
string imageFilePath = Path.Combine("GeneratePreviewFolder", "image-" + pageNumber.ToString() + ".jpg");
var folder = Path.GetDirectoryName(imageFilePath);
if(!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
return new System.IO.FileStream(imageFilePath, FileMode.Create);
}
private static void ReleasePageStream(int pageNumber, Stream pageStream)
{
pageStream.Dispose();
string imageFilePath = Path.Combine("GeneratePreviewFolder", "image-" + pageNumber.ToString() + ".jpg");
Console.WriteLine("Image file {0} is ready for preview", imageFilePath);
}
NoteNOTE: Stream that was created over CreatePageStream delegate will be disposed automatically once after generation of preview image. If you need to implement custom image preview stream disposing you have to pass additional argument ReleasePageStream to clean up resources.
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