public static Bitmap GenerateTemplatePreview(this DocumentTemplate DocumentTemplate, DiscoDataContext Database, int Width, int PageGapHeight, bool DrawPageBorder)
{
string filename = DocumentTemplate.RepositoryFilename(Database);
if (File.Exists(filename))
{
using (var fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read))
{
using (var pdfDocument = PdfiumViewer.PdfDocument.Load(fileStream))
{
var pageMaxWidth = (int)pdfDocument.PageSizes.Max(s => s.Width);
var pageScale = (float)(Width + (DrawPageBorder ? -2 : 0)) / pageMaxWidth;
var previewTotalHeight = pdfDocument.PageSizes
.Take(40)
.Select(s => (int)(pageScale * s.Height))
.Sum() +
(DrawPageBorder ? (Math.Min(40, pdfDocument.PageCount) * 2) : 0) +
((Math.Min(40, pdfDocument.PageCount) - 1) * PageGapHeight);
var result = new Bitmap(Width, previewTotalHeight);
result.SetResolution(72, 72);
using (var graphics = Graphics.FromImage(result))
{
var yPosition = 0;
for (int pageIndex = 0; pageIndex < Math.Min(40, pdfDocument.PageCount); pageIndex++)
{
var pageSize = pdfDocument.PageSizes[pageIndex];
var previewWidth = Math.Floor(pageScale * pageSize.Width);
var previewHeight = Math.Floor(pageScale * pageSize.Height);
// Calculate box
var destination = new Rectangle(
x: (int)((Width - previewWidth) / 2),
y: yPosition + (DrawPageBorder ? 1 : 0),
width: (int)previewWidth,
height: (int)previewHeight
);
// Fill white background
graphics.FillRectangle(Brushes.White, destination);
using (var image = pdfDocument.Render(pageIndex, (int)previewWidth, (int)previewHeight, 72F, 72F, false))
{
graphics.DrawImage(image, destination.X, destination.Y);
}
if (DrawPageBorder)
{
destination.X -= 1;
destination.Y -= 1;
destination.Width += 1;
destination.Height += 1;
graphics.DrawRectangle(Pens.LightGray, destination);
}
yPosition += destination.Height + PageGapHeight;
}
}
return result;
}
}
}
return null;
}