Pdfium.Net.Free 一个免费的Pdfium的 .net包装器--PDF预览器框选

项目地址：

Pdfium.Net：https://github.com/1000374/Pdfium.Net

PdfiumViewer：https://github.com/1000374/PdfiumViewer

框选PDF坐标及区域内文字：

关键代码：

//选中区域的坐标转成相对于pdf的坐标 
var point1 = this.PointToPdf(new Point(_currRect.X, _currRect.Y));
 var point2 = this.PointToPdf(e.Location);
 int x = (int)point1.Location.X;
 int y = (int)point2.Location.Y;
 int x1 = (int)point2.Location.X;
 int y1 = (int)point1.Location.Y;
 var txt = this.Document.Pages[Page].GetBoundedText(x, y, x1, y1);
 _currRect = Rectangle.Empty;
 if (Math.Abs(x1 - x) * Math.Abs(y1 - y) == 0)//相当与未框选有效区域
     return;
 BoundedTextHandler?.Invoke(Page, x, y, x1, y1, txt, true);

 截取pdf指定区域的图片：

关键代码：

//选中区域的坐标转成相对于pdf的坐标 

 var point1 = this.PointToPdf(new Point(_currRect.X, _currRect.Y));
 var point2 = this.PointToPdf(e.Location);

 var bound = Document.Pages[Page].PageSize;
 var rect = new Rectangle();
 var x = (int)point1.Location.X;
 var y = (int)Math.Abs(bound.Height - point1.Location.Y);
 var x1 = (int)point2.Location.X;
 var y1 = (int)Math.Abs(bound.Height - point2.Location.Y);

 rect.X = Math.Min(x, x1);
 rect.Y = Math.Min(y, y1);
 rect.Width = Math.Abs(x1 - x);
 rect.Height = Math.Abs(y1 - y);
 _currRect = Rectangle.Empty;
 if (Math.Abs(x1 - x) * Math.Abs(y1 - y) == 0)//相当与未框选有效区域
     return;

 var image = Document.Render(
                     Page,
                     (int)Document.Pages[Page].Width,
                     (int)Document.Pages[Page].Height,
                    rect.X, // x of the top/left of clipping rectangle
                    rect.Y, // y of the top/left point of clipping rectangle
                    rect.Width, // width of clipping reactangle
                    rect.Height, // height of clipping reactangle
                    _cutDpiX,
                    _cutDpiY,
                    FpdfRotation.Rotate0, // no rotation
                    RenderFlags.None // no render flags
                                        );
 BoundedCutHandler?.Invoke(Page, rect, image);

 转换出来的效果：