Sets the alpha to a specified value in a given rectangle.
#Include <WinAPIEx.au3>
_WinAPI_BufferedPaintSetAlpha ( $hBP [, $iAlpha [, $tRECT]] )
| $hBP | Handle of the buffered paint context. |
| $iAlpha | [可选参数] The alpha value to set. The alpha value can range from zero (fully transparent) to 255 (fully opaque). |
| $tRECT | [可选参数] $tagRECT structure that specifies the rectangle in which to set the alpha. If this parameter is 0, the entire buffer is used. |
| 成功: | 返回 1. |
| 失败: | 返回 0 并设置 @error 标志为非 0 值, @extended 标志可能包含一个系统错误代码. |
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