提高 iPhone 上 pdf 渲染的性能
我有一个 UITableView，在每个单元格中都显示了一个从 pdf 创建的 UIImage。但现在的表现却非常糟糕。这是我用来从 PDF 生成 UIImage 的代码。
创建 CGPDFDocumentRef 和 UIImageView（在 cellForRowAtIndexPath 方法中）：
...
CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), (CFStringRef)formula.icon, NULL, NULL);
CGPDFDocumentRef documentRef = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
CFRelease(pdfURL);
UIImageView *imageView = [[UIImageView alloc] initWithImage:[self imageFromPDFWithDocumentRef:documentRef]];
...
生成 UIImage：
- (UIImage *)imageFromPDFWithDocumentRef:(CGPDFDocumentRef)documentRef {
CGPDFPageRef pageRef = CGPDFDocumentGetPage(documentRef, 1);
CGRect pageRect = CGPDFPageGetBoxRect(pageRef, kCGPDFCropBox);
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, CGRectGetMinX(pageRect),CGRectGetMaxY(pageRect));
CGContextScaleCTM(context, 1, -1);
CGContextTranslateCTM(context, -(pageRect.origin.x), -(pageRect.origin.y));
CGContextDrawPDFPage(context, pageRef);
UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return finalImage;
}
我可以做些什么来提高速度并保持较低的内存？
I have a UITableView, and in every cell there's displayed a UIImage created from a pdf. But now the performance is very bad. Here's my code I use to generate the UIImage from the PDF.
Creating CGPDFDocumentRef and UIImageView (in cellForRowAtIndexPath method):
...
CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), (CFStringRef)formula.icon, NULL, NULL);
CGPDFDocumentRef documentRef = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL);
CFRelease(pdfURL);
UIImageView *imageView = [[UIImageView alloc] initWithImage:[self imageFromPDFWithDocumentRef:documentRef]];
...
Generate UIImage:
- (UIImage *)imageFromPDFWithDocumentRef:(CGPDFDocumentRef)documentRef {
CGPDFPageRef pageRef = CGPDFDocumentGetPage(documentRef, 1);
CGRect pageRect = CGPDFPageGetBoxRect(pageRef, kCGPDFCropBox);
UIGraphicsBeginImageContext(pageRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, CGRectGetMinX(pageRect),CGRectGetMaxY(pageRect));
CGContextScaleCTM(context, 1, -1);
CGContextTranslateCTM(context, -(pageRect.origin.x), -(pageRect.origin.y));
CGContextDrawPDFPage(context, pageRef);
UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return finalImage;
}
What can I do to increas the speed and keep the memory low?
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在运行时为每个单元格生成 PDF 图像似乎对性能造成了巨大影响。
您应该尝试考虑在后台线程中执行实际渲染并存储渲染结果 UIImages 并在运行时将它们填充到 UITableView 中。这至少会释放 UI 线程并增加应用程序的响应能力。
对于尚未渲染的单元格，您可以显示“正在加载”消息或添加“活动指示器”微调器。
Generating image from PDF for each cell in runtime seems like a huge performance hit.
You should try to consider maybe performing the actual rendering in the background thread and store the rendered result
UIImagesand populate them into theUITableViewin runtime. This will at-least free up the UI thread and add responsiveness to application.For the cells that are not yet rendered you can display a 'loading' message or add a 'activity indicator' spinner.