最近在整理代碼的時候發現了這個函數,但是原作者是誰我已經不知道了,修正了里面的一個bug,然后把alpha修改為0-255個級別!(原來為10)

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?1?procedure?DrawAlpha(bmpBack,?bmpFore?:?TBitmap;?TransColor?:?TColor;?OffX,?OffY?:?Integer;?Alpha?:?Integer);
?2?
?3?type
?4???TRGBArray?=?array[0..32767]?of?TRGBTriple;
?5???PRGBArray?=?^TRGBArray;
?6?
?7?var
?8???X,?Y?????:?Integer;
?9???rowFore,
10???rowBack??:?PRGBArray;
11?
12?begin
13???//?check?bitmaps
14???if?not?Assigned(bmpBack)?or
15??????not?Assigned(bmpFore)?then
16????Exit;
17?
18???//?check?color?depth
19???if?(bmpFore.PixelFormat?<>?pf24bit)?or
20??????(bmpBack.PixelFormat?<>?pf24bit)?then
21????Exit;
22?
23?//?check?dimensions
24?//??if?(bmpFore.Height?+?OffY?>?bmpBack.Height)?or
25?//?????(bmpFore.Width?+?OffX?>?bmpBack.Width)?then
26?//????Exit;
27?
28???//?check?alpha?value
29???if?(Alpha?>?255)?or
30??????(Alpha?<?0)?then
31?????Alpha?:=?255;
32?
33???for?y?:=?0?to?bmpFore.Height?-?1?do
34???begin
35?????//?scan?bitmap?rows
36?????if?(y?>?bmpBack.Width)?then
37???????????Continue;
38?????rowBack?:=?bmpBack.ScanLine[y?+?OffY];
39?????rowFore?:=?bmpFore.ScanLine[y];
40?????for?x?:=?0?to?bmpFore.Width?-?1?do
41?????begin
42?????if?(x+offx>bmpBack.Width)?then
43???????????Continue;
44?????//?if?not?transparent?color
45?????if?not?((rowFore[x].rgbtRed???=?GetRValue(TransColor))?and
46?????????????(rowFore[x].rgbtGreen?=?GetGValue(TransColor))?and
47?????????????(rowFore[x].rgbtBlue??=?GetBValue(TransColor)))?then
48?????//?calculate?new?pixel?value
49?????begin
50???????rowBack[x?+?OffX].rgbtRed???:=?((rowBack[x?+?OffX].rgbtRed?*?(255?-?Alpha))???+?(rowFore[x].rgbtRed?*?abs(Alpha-255)))div?255;
51???????rowBack[x?+?OffX].rgbtGreen?:=?((rowBack[x?+?OffX].rgbtGreen)?*?(255?-?Alpha)?+?(rowFore[x].rgbtGreen?*?Abs(Alpha-255)))div?255;
52???????rowBack[x?+?OffX].rgbtBlue??:=?((rowBack[x?+?OffX].rgbtBlue)?*?(255?-?Alpha)??+?(rowFore[x].rgbtBlue?*?Abs(Alpha-255)))div?255;
53?????end;
54???end;
55???end;
56?end;

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下面的是使用的例子

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?1?procedure?TForm1.Button2Click(Sender:?TObject);
?2?begin
?3???//?set?color?depth?to?16.7mio?colors?(24?bit)
?4???//?because?the?loaded?bitmaps?are?8?bit
?5???img1.Picture.Bitmap.PixelFormat?:=?pf24bit;
?6???img2.Picture.Bitmap.PixelFormat?:=?pf24bit;
?7?
?8???DrawAlpha(img1.Picture.Bitmap,?img2.Picture.Bitmap,?clFuchsia,?10,?10,?5);
?9?
10???//?update?image1?(result)
11???img1.Invalidate;
12?end;

?

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轉載于:https://www.cnblogs.com/sun_catboy/archive/2008/09/16/1291579.html

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