iOS常用小功能（获得屏幕图像、压缩图片、加边框、调整label的size）

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

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• 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]