使用按位枚举 EXIF 闪存可读字符串

Question

当你用PHP从图像中提取EXIF数据时，它有一个Flash值，它是一个整数。

例如，16转换为十六进制时为 0x10 .这意味着闪光灯已关闭，闪光灯未闪光：

0x0     = No Flash
0x1     = Fired
0x5     = Fired, Return not detected
0x7     = Fired, Return detected
0x8     = On, Did not fire
0x9     = On, Fired
0xd     = On, Return not detected
0xf     = On, Return detected
0x10    = Off, Did not fire
0x14    = Off, Did not fire, Return not detected
0x18    = Auto, Did not fire
0x19    = Auto, Fired
0x1d    = Auto, Fired, Return not detected
0x1f    = Auto, Fired, Return detected
0x20    = No flash function
0x30    = Off, No flash function
0x41    = Fired, Red-eye reduction
0x45    = Fired, Red-eye reduction, Return not detected
0x47    = Fired, Red-eye reduction, Return detected
0x49    = On, Red-eye reduction
0x4d    = On, Red-eye reduction, Return not detected
0x4f    = On, Red-eye reduction, Return detected
0x50    = Off, Red-eye reduction
0x58    = Auto, Did not fire, Red-eye reduction
0x59    = Auto, Fired, Red-eye reduction
0x5d    = Auto, Fired, Red-eye reduction, Return not detected
0x5f    = Auto, Fired, Red-eye reduction, Return detected

有没有办法在 PHP 中使用按位枚举它，以便可以返回可读的字符串。

例如，0x19的值 25 可能如下所示(并且似乎有效(：

$fired = 0x01;
$auto = 0x18;
$flashValue = dechex(25); // 0x19
$parts = [];
if ($flashValue & $fired)
{
    $parts[] = 'Fired';
}
if ($flashValue & $auto)
{
    $parts[] = 'Auto';
}
$string = implode(', ', $parts); // "Fired, Auto"

这似乎有效，但诸如原始示例之类的示例我似乎无法工作。

Answer 1

$flashValue = dechex(25); // 0x19

不要使用dechex() .它返回一个字符串;您尝试使用的按位运算符对数字进行操作。(25是一个非常好的数字 - 你没有用十六进制写它的事实并不重要。

您必须处理的一个复杂问题是"auto"是标志的奇怪组合：0x08是"关闭"，0x10是"打开"，并且将两者组合在一起(0x10 + 0x08 = 0x18(会给你"自动"。您需要仔细处理这些。