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 output stream creation (see event handler CreatePageStream);
- image preview format - PNG / JPG / BMP;
- page numbers to process;
- custom size of preview images (if needed). NoteOutputStream 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 OutputStream createPageStream(int pageNumber)
{
try{
String imageFilePath = new File("GeneratePreviewFolder", "image-" + pageNumber + ".jpg").getPath();
return new FileOutputStream(imageFilePath);
}catch (Exception e){
throw new GroupDocsException(e.getMessage());
}
}
private static void releasePageStream(int pageNumber, OutputStream pageStream)
{
try {
pageStream.close();
String imageFilePath = new File("GeneratePreviewFolder", "image-" + pageNumber + ".jpg").getPath();
System.out.print("Image file "+imageFilePath+" is ready for preview.");
}catch (Exception e){
throw new GroupDocsException(e.getMessage());
}
}
public static void getPreview()
{
string filePath = "c:\sample.xlsx";
Merger merger = new Merger(filePath);
IPreviewOptions previewOption = new PreviewOptions(new CreatePageStream() {
@Override
public OutputStream invoke(int pageNumber) {
return createPageStream(pageNumber);
}
}, PreviewMode.JPEG);
merger.generatePreview(previewOption);
}
private static OutputStream createPageStream(int pageNumber)
{
try{
String imageFilePath = new File("GeneratePreviewFolder", "image-" + pageNumber + ".jpg").getPath();
return new FileOutputStream(imageFilePath);
}catch (Exception e){
throw new GroupDocsException(e.getMessage());
}
}
public static void getPreview()
{
string filePath = "c:\sample.xlsx";
Merger merger = new Merger(filePath);
IPreviewOptions previewOption = new PreviewOptions(new CreatePageStream() {
@Override
public OutputStream invoke(int pageNumber) {
return createPageStream(pageNumber);
}
}, new ReleasePageStream() {
@Override
public void invoke(int pageNumber, OutputStream pageStream) {
releasePageStream(pageNumber, pageStream);
}
}, PreviewMode.JPEG);
merger.generatePreview(previewOption);
}
private static OutputStream createPageStream(int pageNumber)
{
try{
String imageFilePath = new File("GeneratePreviewFolder", "image-" + pageNumber + ".jpg").getPath();
return new FileOutputStream(imageFilePath);
}catch (Exception e){
throw new GroupDocsException(e.getMessage());
}
}
private static void releasePageStream(int pageNumber, OutputStream pageStream)
{
try {
pageStream.close();
String imageFilePath = new File("GeneratePreviewFolder", "image-" + pageNumber + ".jpg").getPath();
System.out.print("Image file "+imageFilePath+" is ready for preview.");
}catch (Exception e){
throw new GroupDocsException(e.getMessage());
}
}
private static String getImagePath(int pageNumber)
{
return Constants.OutputPath +"GeneratePreview\\image-"+pageNumber+".jpg";
}
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 ReleasePageStreamto clean up resources.
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