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Posted 1 Feb 2000

Using the AlphaBlend function

, 1 Feb 2000
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A sample application that uses the AlphaBlend function to produce a transparent splash screen
  • Download source files - 35 Kb
  • Sample Image - alphablend.gif

    <!-- Article Starts --> Note: The code in this article is restricted to win98 and win2000

    Do you want to cool splash window?. Do you think the general splash window is not good enough for your app? Then this sample source is for you.

    My semi-transparent splash window uses the AlphaBlend function. When I found this function, I was so surprised! The function works just like BitBlt for bitmaps that have transparent or semitransparent pixels. Here is the AlphaBlend function's syntax

    BOOL AlphaBlend( HDC hdcDest,
      int nXOriginDest,
      int nYOriginDest,
      int nWidthDest,
      int nHeightDest,
      HDC hdcSrc,
      int nXOriginSrc,
      int nYOriginSrc,
      int nWidthSrc,
      int nHeightSrc,
      BLENDFUNCTION blendFunction

    The important parameter is last one, BLENDFUNCTION.

    typedef struct _BLENDFUNCTION {
        BYTE     BlendOp;
        BYTE     BlendFlags;
        BYTE     SourceConstantAlpha;
        BYTE     AlphaFormat;
    • BlendOp must be AC_SRC_OVER
    • BlendFlags must be 0
    • SourceConstantAlpha must be between 0 (transparent) and 255 (semi-transparent).
    • AlphaFormat must be AC_SRC_ALPHA
    MSND states:  The SourceConstantaAlpha member of BLENDFUNCTION specifies an alpha transparancy value to be used on the entire source bitmap. The SourceConstantAlpha value is combined with any per-pixel alpha values. If you set SourceConstantAlpha to 0, it is assumed that your image is transparent. Set the SourceConstantAlpha value to 255 (indicates that the image is opaque) when you only want to use per-pixel alpha values.

    See the sample application for a demonstration.

    Just enjoy!!

    Ajou University C.C. 4th member.


    This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

    A list of licenses authors might use can be found here


    About the Author

    Wooseok Seo
    Software Developer (Senior)
    Korea (Republic of) Korea (Republic of)
    Woo Seok Seo have been a Microsoft MVP for 7 years and have translated several books into Korean. Author of C# Programming for Beginner (DevPress, 2001), he is interested in Debugging techniques and .NET technology. Get in touch with Woo Seok Seo at

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    Comments and Discussions

    QuestionGotcha with 64-bit OS and AlphaBlend Pin
    Snuff Daddy12-Jun-15 12:33
    memberSnuff Daddy12-Jun-15 12:33 
    QuestionAlphaBlend mode using Borland C++ 5.0 Pin
    Member 1091480330-Jun-14 8:33
    memberMember 1091480330-Jun-14 8:33 
    GeneralMy vote of 3 Pin
    Mahdi Nejadsahebi30-Apr-11 21:24
    groupMahdi Nejadsahebi30-Apr-11 21:24 
    GeneralMy vote of 2 Pin
    Member 3186846-Jan-10 0:41
    memberMember 3186846-Jan-10 0:41 
    QuestionAlphaBlend draws over the existing backgruound making it darker. gradually losing transaprency Pin
    VC++Maniac20-Apr-09 21:15
    memberVC++Maniac20-Apr-09 21:15 
    AnswerRe: AlphaBlend draws over the existing backgruound making it darker. gradually losing transaprency Pin
    Snuff Daddy12-Jun-15 12:41
    memberSnuff Daddy12-Jun-15 12:41 
    GeneralAbout OnPaint with the AlphaBlend(); [modified] Pin
    Ted Lin16-Aug-07 22:12
    memberTed Lin16-Aug-07 22:12 
    GeneralAlphaBlend wrong formula ?! Pin
    Octopod23-Sep-06 10:17
    memberOctopod23-Sep-06 10:17 
    GeneralRe: AlphaBlend wrong formula ?! Pin
    Octopod23-Sep-06 10:50
    memberOctopod23-Sep-06 10:50 
    GeneralThank you Pin
    Nick Z.23-May-05 10:41
    memberNick Z.23-May-05 10:41 
    GeneralProblem with AlphaBlend Pin
    acidutzu23-Mar-05 23:13
    memberacidutzu23-Mar-05 23:13 
    GeneralRe: Problem with AlphaBlend Pin
    jgarnett27-Oct-05 15:59
    memberjgarnett27-Oct-05 15:59 
    GeneralRe: Problem with AlphaBlend Pin
    Snuff Daddy12-Jun-15 12:31
    memberSnuff Daddy12-Jun-15 12:31 
    GeneralQuestion Pin
    one_eddie1-Oct-04 11:40
    memberone_eddie1-Oct-04 11:40 
    GeneralGreat stuff! Pin
    JustDan24-Jan-04 17:36
    memberJustDan24-Jan-04 17:36 
    GeneralRe: Great stuff! Pin
    anothermxw4-Apr-04 19:08
    memberanothermxw4-Apr-04 19:08 
    GeneralRe: Great stuff! Pin
    Anonymous5-Apr-04 14:18
    sussAnonymous5-Apr-04 14:18 
    GeneralNo with Dialog Pin
    mojster17-May-03 5:42
    membermojster17-May-03 5:42 
    GeneralAlgorithm Code Pin
    Jack Rabbit27-Feb-03 17:34
    memberJack Rabbit27-Feb-03 17:34 
    GeneralRe: Algorithm Code Pin
    Henry P.27-Feb-03 17:57
    memberHenry P.27-Feb-03 17:57 
    GeneralRe: Algorithm Code Pin
    Jack Rabbit28-Feb-03 19:38
    memberJack Rabbit28-Feb-03 19:38 
    GeneralRe: Algorithm Code Pin
    Anonymous3-Mar-03 6:27
    sussAnonymous3-Mar-03 6:27 
    GeneralRe: Algorithm Code Pin
    Jack Rabbit8-Mar-03 4:50
    memberJack Rabbit8-Mar-03 4:50 
    GeneralRe: Algorithm Code Pin
    Henry P.31-Mar-03 19:22
    memberHenry P.31-Mar-03 19:22 
    GeneralRe: Algorithm Code Pin
    B2kguga25-Feb-07 10:04
    memberB2kguga25-Feb-07 10:04 

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