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);
}
Use the Width and Height properties of PreviewOptions to get preview images of a specific size in pixels. The size is honoured for every supported document format:
- When both
WidthandHeightare set, every preview image has exactly that size. - When only one of them is set, the other is calculated from the page’s aspect ratio.
- A negative
WidthorHeightthrowsGroupDocsMergerException.
The Resolution property sets the resolution of the rendered images.
public static void GetPreviewOfSize()
{
string filePath = @"c:\sample.docx";
using (Merger merger = new Merger(filePath))
{
PreviewOptions previewOption = new PreviewOptions(CreatePageStream, PreviewMode.JPEG);
// Every preview image will be 800 pixels wide; the height follows the page's aspect ratio
previewOption.Width = 800;
merger.GeneratePreview(previewOption);
}
}
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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