iOS 关于在图片上绘制文字导致图片失真的解决方案

由于业务需要, 图片需要更新文本, 而此图片又需要保存. 所以使用图片上绘制文字. (也就是UIview 转 UIImageView).

但是这种情况下, 在retain 高清屏显示的时候, 会出现图片像素降低, 失真的情况.

故而找了一下解决方案, 在此记录一下.

//图片添加文字
+ (UIImage )imageWithText:(NSString )text
textFont:(NSInteger)fontSize
textColor:(UIColor *)textColor
textFrame:(CGRect)textFrame
originImage:(UIImage *)image
imageLocationViewFrame:(CGRect)viewFrame {

if (!text)      {  return image;   }
if (!fontSize)  {  fontSize = 15;   }
if (!textColor) {  textColor = [UIColor blackColor];   }
if (!image)     {  return nil;  }
if (viewFrame.size.height==0 || viewFrame.size.width==0 || textFrame.size.width==0 || textFrame.size.height==0 ){return nil;}

NSString *mark = text;
CGFloat height = [mark sizeWithPreferWidth:textFrame.size.width font:[UIFont systemFontOfSize:fontSize]].height; //    CGFloat height

= [mark sizeWithPreferWidth:textFrame.size.width font:[UIFont fontWithName:@”huakanghaibao” size:fontSize]].height;

if ((height + textFrame.origin.y) > viewFrame.size.height) { // 文字高度超出父视图的宽度
    height = viewFrame.size.height - textFrame.origin.y;
}

//    CGFloat w = image.size.width;
//    CGFloat h = image.size.height; 
//这个函数是最初使用的, 导致图片失真. 
//    UIGraphicsBeginImageContext(viewFrame.size);
//替换这个解决图片失真
UIGraphicsBeginImageContextWithOptions(viewFrame.size, NO, [UIScreen mainScreen].scale);
[image drawInRect:CGRectMake(0, 0, viewFrame.size.width, viewFrame.size.height)];
NSDictionary *attr = @{NSFontAttributeName: [UIFont systemFontOfSize:fontSize], NSForegroundColorAttributeName : textColor

};
//位置显示
CGFloat tWidth = [self getWidthWithTitle:mark font:[UIFont systemFontOfSize:fontSize]];
CGFloat t1x = 0.0;
//文本位置
t1x = (image.size.width / 2) - (tWidth) / 2;

[mark drawInRect:CGRectMake(/*textFrame.origin.x*/t1x, textFrame.origin.y, tWidth/*textFrame.size.width*/, height)

withAttributes:attr];

UIImage *aimg = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return aimg; }