Save the image data for an item.
protected abstract void SaveItem(
ImageViewerItem item,
object data
)
protected:
virtual void SaveItem(
ImageViewerItem^ item,
Object^ data
) abstract
item
Source item
data
The image object for this item.
This method is called when an item is about to be deleted from the cache. This gives the derived class the opportunity to serialize the data to disk or a database if needed.
data is the same object returned from LoadItem for this item.
You should encapsulate the code inside this method with a try/catch and handle the error correctly. This method will not automatically fire the ItemError event.
using Leadtools;
using Leadtools.Controls;
using Leadtools.Codecs;
using Leadtools.Drawing;
public ImageViewerForm _form = new ImageViewerForm();
public ImageViewer _imageViewer;
public void ImageViewerVirtualizerExample()
{
// Get the input file name
string _imageFileName = imageFileName;
// Get the ImageViewer control from the form
_imageViewer = _form.ImageViewer;
// Set to vertical view layout
_imageViewer.ViewLayout = new ImageViewerVerticalViewLayout();
// Add pan zoom interactive mode
_imageViewer.InteractiveModes.Add(new ImageViewerPanZoomInteractiveMode());
// Add empty items, each one with the correct size but with no image data
// The virtualizer will take care of loading the pages and rendering them
using (RasterCodecs codecs = new RasterCodecs())
{
int pageCount;
LeadSize pageSize;
LeadSizeD pageResolution;
using (CodecsImageInfo info = codecs.GetInformation(_imageFileName, true))
{
pageCount = info.TotalPages;
pageSize = LeadSize.Create(info.Width, info.Height);
pageResolution = LeadSizeD.Create(info.XResolution, info.YResolution);
}
_imageViewer.BeginUpdate();
for (int page = 1; page <= pageCount; page++)
{
ImageViewerItem item = new ImageViewerItem();
item.ImageSize = pageSize;
item.Resolution = pageResolution;
_imageViewer.Items.Add(item);
}
_imageViewer.EndUpdate();
// Set the virtualizer to start loading the data into the empty items
_imageViewer.Virtualizer = new MyVirtualizer(_imageFileName);
// Hook to the VirtualizeItemReady to log each item as its image data is loaded
_imageViewer.VirtualizeItemReady += (Object sender, ImageViewerVirtualizerEventArgs e) =>
{
System.Diagnostics.Debug.WriteLine("Image data for page " + (e.Item.RowIndex + 1) + " is ready");
};
}
}
// Custom Virtualizer
public class MyVirtualizer : ImageViewerVirtualizer
{
private string _imageFileName;
public MyVirtualizer(string imageFileName) : base()
{
_imageFileName = imageFileName;
// Load 4 items at a time
this.MaximumItems = 4;
}
protected override object LoadItem(ImageViewerItem item)
{
// Load a page, the page number is the item index, but it
// could be anything in the application, for example
// using ImageViewerItem.Tag to store the necessary data to identity this item
int pageNumber = this.ImageViewer.Items.IndexOf(item);
using (RasterCodecs codecs = new RasterCodecs())
{
return codecs.Load(_imageFileName, pageNumber);
}
}
protected override void SaveItem(ImageViewerItem item, object data)
{
// Nothing to do in this application, just log it.
// If save is required, then this is the place to do it
int pageNumber = this.ImageViewer.Items.IndexOf(item);
System.Diagnostics.Debug.WriteLine("SaveItem for page " + pageNumber + " is called");
}
protected override void DeleteItem(ImageViewerItem item, object data)
{
// Dispose the image
RasterImage image = data as RasterImage;
if (image != null)
image.Dispose();
}
protected override void RenderItemPlaceholder(ImageViewerRenderEventArgs e)
{
// Render the placeholder for this page
int pageNumber = this.ImageViewer.Items.IndexOf(e.Item) + 1;
LeadMatrix transform = this.ImageViewer.GetItemImageTransform(e.Item);
Graphics graphics = e.PaintEventArgs.Graphics;
// Render the message at 0,0 in this item transformation
LeadPointD pt = LeadPointD.Create(0, 0);
pt = transform.Transform(pt);
string message = string.Format("Loading page {0}...", pageNumber);
graphics.DrawString(message, this.ImageViewer.Font, Brushes.Black, (float)pt.X, (float)pt.Y);
}
}
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