如何在iOS上使用CoreGraphics渲染的pdf转换文本颜色? [英] How would I invert text color on a pdf rendered with CoreGraphics on iOS?
问题描述
我正在使用开源PDF查看库(VFR PDF Reader https://github.com/vfr/读者)。我正在尝试实现夜间模式或带有白色文本的黑色背景。我可以将背景设置为任何喜欢的颜色,但是无法更改文字颜色。您可以在 https:// github上看到可以修改背景颜色的位置。 com / vfr / Reader / blob / master / Sources / ReaderContentPage.m 中的 drawLayer方法。它只是在更改呈现PDF的矩形的颜色。
I am using an open-source PDF viewing library (VFR PDF Reader https://github.com/vfr/Reader). I'm trying to implement "night mode" or black background with white text. I can get the background to any color I like but I can't get the text color to change. You can see where you can modify the background color at https://github.com/vfr/Reader/blob/master/Sources/ReaderContentPage.m in the "drawLayer" method. It is simply changing the color of the rectangle the PDF is rendered on.
我的问题是:是否可以对上下文执行某些操作,以使pdf中的文本更改颜色(在我的情况下,我希望使用白色文本) ?问题所在的行看起来像这样(行558):
My question is: is there something I can do to the "context" that would cause the text in the pdf to change color (in my case I want white text)? The line in question looks like this (line 558):
CGContextDrawPDFPage(context, _PDFPageRef); // Render the PDF page into the context
推荐答案
我解决夜视的方法:
1)我在NSUserDefault中跟踪用户的偏好(夜间模式或白天模式)
1)I keep track of user preference (night mode or Day mode) in NSUserDefault
2)在
- (void)drawLayer:(CATiledLayer *)layer inContext:(CGContextRef)context
{
a)检索用户首选项
NSString *userViewMode = [[NSUserDefaults standardUserDefaults] objectForKey:@"DayOrNightSetting"];
b)将CGContextRef的背景色设置为白色
b) set the back ground color of the CGContextRef to white
CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
c)将CGContextDrawPage(Context,_PDFPageRef)替换为:
c) replace CGContextDrawPage(Context,_PDFPageRef) with :
if ([userViewMode isEqualToString:@"Night"]) {
CGContextSetBlendMode(context, kCGBlendModeDestinationAtop);
CGContextDrawPDFPage(context, _PDFPageRef);
CGContextSetBlendMode(context, kCGBlendModeExclusion);
CGContextDrawPDFPage(context, _PDFPageRef);
}
else
{
CGContextSetBlendMode(context,kCGBlendModeNormal);
CGContextDrawPDFPage(context, _PDFPageRef);
}
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