iOS开发 RGBA转16进制

代码

• 当hexString = @"ffffff",默认的alpha值为1
• 当hexString = @"ffffff7f",则alpha值为0.5

+ (UIColor *)colorWithString:(NSString *)hexString {
    NSString *hex = [NSString stringWithString:hexString];
    if ([hex hasPrefix:@"#"]) hex = [hex substringFromIndex:1];
    if (hex.length == 6) {
        hex = [hex stringByAppendingString:@"FF"];
    } else if (hex.length != 8) return nil;
    uint32_t rgba;
    NSScanner *scanner = [NSScanner scannerWithString:hex];
    [scanner scanHexInt:&rgba];
    return [UIColor colorWithRed:((rgba >> 24)&0xFF) / 255. green:((rgba >> 16)&0xFF) / 255. blue:((rgba >> 8)&0xFF) / 255. alpha:(rgba&0xFF) / 255.];
}

十六进制alpha含义