iOS常用小功能（获得屏幕图像、压缩图片、加边

摘要：获得屏幕图像,label的动态size,时间戳转化为时间,RGB转化成颜色,加边框,压缩图片,textfield的placeholder,图片做灰度处理

1.获得屏幕图像

- (UIImage *)imageFromView: (UIView *) theView
{
  UIGraphicsBeginImageContext(theView.frame.size);
  CGContextRef context = UIGraphicsGetCurrentContext();
  [theView.layer renderInContext:context];
  UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return theImage;
}

2.label的动态size

- (CGSize)labelAutoCalculateRectWith:(NSString*)text FontSize:(CGFloat)fontSize MaxSize:(CGSize)maxSize
{
  NSMutableParagraphStyle* paragraphStyle = [[NSMutableParagraphStyle alloc]init]; paragraphStyle.lineBreakMode=NSLineBreakByWordWrapping;
  NSDictionary* attributes =@{NSFontAttributeName:[UIFont fontWithName:@"MicrosoftYaHei" size:fontSize],NSParagraphStyleAttributeName:paragraphStyle.copy};
  CGSize labelSize = [text boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading|NSStringDrawingTruncatesLastVisibleLine attributes:attributes context:nil].size;
  labelSize.height=ceil(labelSize.height);
  return labelSize;
}

3.时间戳转化为时间

-(NSString*)TimeTrasformWithDate:(NSString *)dateString
{
  NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
  [formatter setDateFormat:@"YY-MM-dd HH:mm"];
  [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"Asia/Beijing"]];

  NSString *date = [formatter stringFromDate:[NSDate dateWithTimeIntervalSince1970:dateString.integerValue]];
  //NSLog(@"date1:%@",date);
  return date;
}

4.RGB转化成颜色

+ (UIColor *)colorFromHexRGB:(NSString *)inColorString
{
  UIColor *result = nil;
  unsigned int colorCode = 0;
  unsigned char redByte, greenByte, blueByte;
  if (nil != inColorString)
  {
    NSScanner *scanner = [NSScanner scannerWithString:inColorString];
    (void) [scanner scanHexInt:&colorCode]; // ignore error
  }
  redByte = (unsigned char) (colorCode >> 16);
  greenByte = (unsigned char) (colorCode >> 8);
  blueByte = (unsigned char) (colorCode); // masks off high bits
  result = [UIColor
       colorWithRed: (float)redByte / 0xff
       green: (float)greenByte/ 0xff
       blue: (float)blueByte / 0xff
       alpha:1.0];
  return result;
}

5.加边框

UIRectCorner corners=UIRectCornerTopLeft | UIRectCornerTopRight;
  UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds        byRoundingCorners:corners
 cornerRadii:CGSizeMake(4, 0)];
CAShapeLayer *maskLayer = [CAShapeLayer layer];
maskLayer.frame     = view.bounds;
maskLayer.path     = maskPath.CGPath;
view.layer.mask     = maskLayer;

6.//压缩图片

+ (UIImage*)imageWithImageSimple:(UIImage*)image scaledToSize:(CGSize)newSize
{
  //创建一个图形上下文形象
  UIGraphicsBeginImageContext(newSize);
  // 告诉旧图片画在这个新的环境,所需的
  // new size
  [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
  //获取上下文的新形象
  UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
  // 结束上下文
  UIGraphicsEndImageContext();
  return newImage;
}

7.textfield的placeholder

[textF setValue:[UIColor whiteColor] forKeyPath:@"_placeholderLabel.textColor"];
[textF setValue:[UIFont boldSystemFontOfSize:15] forKeyPath:@"_placeholderLabel.font"];

8.布局

butLeft. imageEdgeInsets = UIEdgeInsetsMake (7 , 5 , 7 , 25 );
butLeft.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;

9.//调用此方法改变label最后2个字符的大小

- (void)label:(UILabel *)label BehindTextSize:(NSInteger)integer
{
  NSMutableAttributedString *mutaString = [[NSMutableAttributedString alloc] initWithString:label.text];

  [mutaString addAttribute:NSFontAttributeName value:[UIFont boldSystemFontOfSize:16] range:NSMakeRange(label.text.length-2, 2)];
  label.attributedText = mutaString;
}

10.

- (void)ChangeLabelTextColor:(UILabel *)label
{
  NSMutableAttributedString *mutaString = [[NSMutableAttributedString alloc] initWithString:label.text];
  [mutaString addAttribute:NSForegroundColorAttributeName value:[UIColor colorWithRed:207/255.0 green:34/255.0 blue:42/255.0 alpha:1] range:NSMakeRange(0, 5)];
  label.attributedText = mutaString;
}

if ([tableView respondsToSelector:@selector(setSeparatorInset:)]) {
    [tableView setSeparatorInset:UIEdgeInsetsZero];

  }
  if ([[UIDevice currentDevice].systemVersion floatValue] >= 8.0) {
    if ([tableView respondsToSelector:@selector(setLayoutMargins:)]) {
    [tableView setLayoutMargins:UIEdgeInsetsZero];
  }
  }
  // Do any additional setup after loading the view.
}
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
  if ([cell respondsToSelector:@selector(setSeparatorInset:)]) {
    [cell setSeparatorInset:UIEdgeInsetsZero];
  }
  if ([[UIDevice currentDevice].systemVersion floatValue] >= 8.0) {
    if ([cell respondsToSelector:@selector(setLayoutMargins:)]) {
    [cell setLayoutMargins:UIEdgeInsetsZero];
  }
  }  
}

11.图片变灰度

-(UIImage *) grayscaleImage: (UIImage *) image
{
  CGSize size = image.size;
  CGRect rect = CGRectMake(0.0f, 0.0f, image.size.width,
               image.size.height);
  // Create a mono/gray color space
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
  CGContextRef context = CGBitmapContextCreate(nil, size.width,
                         size.height, 8, 0, colorSpace, kCGImageAlphaNone);
  CGColorSpaceRelease(colorSpace);
  // Draw the image into the grayscale context
  CGContextDrawImage(context, rect, [image CGImage]);
  CGImageRef grayscale = CGBitmapContextCreateImage(context);
  CGContextRelease(context);
  // Recover the image
  UIImage *img = [UIImage imageWithCGImage:grayscale];
  CFRelease(grayscale);
  return img;
}

13.16进制转rgb

#define UIColorFromRGB(rgbValue) [UIColor colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 green:((float)((rgbValue & 0xFF00) >> 8))/255.0 blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]

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