// 完毕:
using System;
using System.IO;
using System.Drawing;
using System.Numerics;
using GrapeCity.Documents.Pdf;
using GrapeCity.Documents.Text;
using GCTEXT = GrapeCity.Documents.Text;
using GCDRAW = GrapeCity.Documents.Drawing;
namespace DsPdfWeb.Demos
{
// This example shows how to use GcGraphics.PushTransparencyLayer()/PopTransparencyLayer() methods
// to specify a common opacity for a group of drawing operations.
// The code is similar to AddWatermark sample, but instead of using a semi-transparent
// text color, it performs all related drawing on a transparency layer.
// This provides a more flexible and convenient approach to control transparency.
public class TransparencyLayer
{
public int CreatePDF(Stream stream)
{
var doc = new GcPdfDocument();
using var fs = File.OpenRead(Path.Combine("Resources", "PDFs", "SlidePages.pdf"));
doc.Load(fs);
foreach (var page in doc.Pages)
{
var g = page.Graphics;
// Text layout used to draw the 'watermark':
var tl = g.CreateTextLayout();
tl.Append("DsPdf Demo");
tl.DefaultFormat.Font = GCTEXT.Font.FromFile(Path.Combine("Resources", "Fonts", "calibrib.ttf"));
tl.DefaultFormat.FontSize = g.Resolution;
tl.DefaultFormat.ForeColor = Color.Blue;
tl.DefaultFormat.GlyphAdvanceFactor = 1.5f;
tl.PerformLayout();
// Rotation angle (radians) - from left/bottom to right/top corners of the page:
var angle = -Math.Asin(g.CanvasSize.Width / g.CanvasSize.Height);
// Page center:
var center = new PointF(g.CanvasSize.Width / 2, g.CanvasSize.Height / 2);
// Additional offset from text size:
var delta = new PointF(
(float)((tl.ContentWidth * Math.Cos(angle) - tl.ContentHeight * Math.Sin(angle)) / 2),
(float)((tl.ContentWidth * Math.Sin(angle) + tl.ContentHeight * Math.Cos(angle)) / 2));
// Create semi-opaque transparency layer. All subsequent drawing operations
// will be drawn using the specified opacity till the PopTransparencyLayer() call:
g.PushTransparencyLayer(null, 0.5f);
// Draw watermark text diagonally in the center of the page
// (matrix transforms are applied from last to first):
g.Transform =
Matrix3x2.CreateRotation((float)angle) *
Matrix3x2.CreateTranslation(center.X - delta.X, center.Y - delta.Y);
g.DrawTextLayout(tl, PointF.Empty);
// Add a border around the text, it will also be drawn semi-transparently:
var rc = new RectangleF(-30, -20, tl.ContentWidth + 60, tl.ContentHeight + 40);
g.DrawRoundRect(rc, 30, new GCDRAW.Pen(Color.DarkOrange, 8));
g.Transform = Matrix3x2.Identity;
// Pop transparency layer:
g.PopTransparencyLayer();
}
doc.Save(stream);
return doc.Pages.Count;
}
}
}