GetPixel函数为什么有时候会返回－1 ？

[tinafang]

为什么呢？大部分时候都可以返回正常的值，但有的时候为什么确返回失败呢？

[dsclub]

The return value is the RGB value of the pixel. If the pixel is outside of the current clipping region, the return value is CLR_INVALID.

Const CLR_INVALID As Long = &HFFFF

Debug.Print CLR_INVALID

结果就是-1了。


Debug.Print Hex(CLR_INVALID)
结果就是FFFFFFFF了。


懂了？

[用户 昵称]

那是因为getpixel返回的long有符号
dim l as long
l = getpixel( ... )
if l < 0 then
l = l + 2^31
end if

[tinafang]

It is when the pixel is outside of the current clipping region that I really want to know !!