将 CGPDFPage 渲染成 UIImage [英] Rendering a CGPDFPage into a UIImage
问题描述
我正在尝试将 CGPDFPage(从 CGPDFDocument 中选择)呈现到 UIImage 中以在视图上显示.
I'm trying to render a CGPDFPage (selected from a CGPDFDocument) into a UIImage to display on a view.
我在 MonoTouch 中有以下代码,这让我有一段路要走.
I have the following code in MonoTouch which gets me part way there.
RectangleF PDFRectangle = new RectangleF(0, 0, UIScreen.MainScreen.Bounds.Width, UIScreen.MainScreen.Bounds.Height);
public override void ViewDidLoad ()
{
UIGraphics.BeginImageContext(new SizeF(PDFRectangle.Width, PDFRectangle.Height));
CGContext context = UIGraphics.GetCurrentContext();
context.SaveState();
CGPDFDocument pdfDoc = CGPDFDocument.FromFile("test.pdf");
CGPDFPage pdfPage = pdfDoc.GetPage(1);
context.DrawPDFPage(pdfPage);
UIImage testImage = UIGraphics.GetImageFromCurrentImageContext();
pdfDoc.Dispose();
context.RestoreState();
UIImageView imageView = new UIImageView(testImage);
UIGraphics.EndImageContext();
View.AddSubview(imageView);
}
显示 CGPDFPage 的一部分,但前后颠倒旋转.我的问题是,如何选择完整的 pdf 页面并将其翻转以正确显示.我看过一些使用 ScaleCTM 和 TranslateCTM 的例子,但似乎无法让它们工作.
A section of the CGPDFPage is displayed but rotated back-to-front and upside down. My question is, how do I select the full pdf page and flip it round to display correctly. I have seen a few examples using ScaleCTM and TranslateCTM but couldn't seem to get them working.
ObjectiveC 中的任何示例都很好,我会尽我所能:)
Any examples in ObjectiveC are fine, I'll take all the help I can get :)
谢谢
推荐答案
我没有使用过 MonoTouch.但是,在 Objective-C 中,您将获得这样的 PDF 页面图像(注意 CTM 转换):
I haven't worked with MonoTouch. However, in objective-C you would get an image for a PDF page like this (notice the CTM transforms):
-(UIImage *)getThumbForPage:(int)page_number{
CGFloat width = 60.0;
// Get the page
CGPDFPageRef myPageRef = CGPDFDocumentGetPage(myDocumentRef, page);
// Changed this line for the line above which is a generic line
//CGPDFPageRef page = [self getPage:page_number];
CGRect pageRect = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
CGFloat pdfScale = width/pageRect.size.width;
pageRect.size = CGSizeMake(pageRect.size.width*pdfScale, pageRect.size.height*pdfScale);
pageRect.origin = CGPointZero;
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
// White BG
CGContextSetRGBFillColor(context, 1.0,1.0,1.0,1.0);
CGContextFillRect(context,pageRect);
CGContextSaveGState(context);
// ***********
// Next 3 lines makes the rotations so that the page look in the right direction
// ***********
CGContextTranslateCTM(context, 0.0, pageRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextConcatCTM(context, CGPDFPageGetDrawingTransform(page, kCGPDFMediaBox, pageRect, 0, true));
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);
UIImage *thm = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return thm;
}
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