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RodBird
Nov 23, 2015
**TransparentBlt** [[user:Alyce]] //For more details on using TransparentBlt, see [[TransparentBlt|Janet Terra's TransparentBltarticle.]] //article.]]// [[toc|flat]]//Some text below is copied from the Microsoft Developers Network Library.// For an eBook or printed book on using the API with Liberty BASIC, see: [[http://alycesrestaurant.com/apilb/index.htm|APIs for Liberty BASIC]] =TransparentBlt= The TransparentBlt function performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context. Like StretchBlt, it can perform a stretching or shrinking of the image. In addition, it makes transparent the color specified. This allows us to place an image directly on any background without a surrounding rectangle, much like sprites. There is one other important difference between StretchBlt and TransparentBlt. StretchBlt is part of the Windows DLL GDI32.DLL. This DLL needn't be opened in Liberty BASIC. It can be addressed directly as #gdi32. The TransparentBlt function is part of MSIMG32.DLL. We must open this DLL in order to use it. [[code format="lb"]] open msimg32.dll for dll as #msimg [[code]] We must close it when we no longer need it. [[code format="lb"]] close #msimg [[code]] =Syntax= [[code format="lb"]] open "Msimg32.dll" for DLL as #msimg CallDll #msimg, "TransparentBlt",_ hdc as ulong,_ 'The destination DC = graphicbox xDest as long,_ 'x location on destination yDest as long,_ 'y location on destination wDest as long,_ 'width to stretch to hDest as long,_ 'height to stretch to hMemDC as ulong,_ 'The source DC = memory xSrc as long,_ 'x location in source ySrc as long,_ 'y location in source wSrc as long,_ 'width to take from source hSrc as long,_ 'height to take from source lColor as ulong,_ 'RGB/long color value to make transparent result asbooleanlong 'nonzero if successful close #msimg [[code]] =Remarks= From MSDN: //If the source and destination rectangles are not the same size, the source bitmap is stretched to match the destination rectangle. When the SetStretchBltMode function is used, the iStretchMode modes of BLACKONWHITE and WHITEONBLACK are converted to COLORONCOLOR for the TransparentBlt function.// //The destination device context specifies the transformation type for the destination coordinates. The source device context specifies the transformation type for the source coordinates.// //TransparentBlt does not mirror a bitmap if either the width or height, of either the source or destination, is negative.// =The Long Color Value= TransparentBlt allows us to specify the color that is to be transparent when the image is transferred. This needs to be in the form of a single, long value. We get this value from the red, green and blue components with the following formula: LongColor = (blue*256*256) + (green*256) + redIf the blue value is 200, green is 100 and red is 10, it looks like this: LongColor = (200*256*256) + (100*256) + 10 =Demo One= The following program demonstrates the transparency of the image when it is transferred. The graphicbox is filled with black and a word is printed on it. The code captures a bitmap from the graphicbox, then fills it with yellow. When the original image is transferred back to the graphicbox, the black is transparent, so the word appears properly on the yellow color. [[code format="lb"]] nomainwin winWide=700:winHigh=500 WindowWidth=winWide+50:WindowHeight=winHigh+50 UpperLeftX=1:UpperLeftY=1 graphicbox #1.g, 0,0,winWide,winHigh open "GDI Demo" for window as #1 #1 "trapclose [quit]" #1.g "down; fill black; backcolor black; color red" #1.g "font arial 20" #1.g "\\\Sample" 'capture a bitmap in memory with native commands #1.g "getbmp display 0 0 160 190" 'get handle for memory bmp handleBmp = hbmp("display") #1.g "fill yellow;flush" h=hwnd(#1.g) 'graphicbox handle 'get device context for window: calldll #user32, "GetDC",_ h as ulong,_ 'graphicbox handle hdc as ulong 'returns handle to device context calldll #gdi32, "CreateCompatibleDC",_ hdc as ulong,_ 'graphicbox DC hMemDC as ulong 'memory DC CallDLL #gdi32,"SelectObject",_ hMemDC as uLong,_ 'memory DC handleBmp as uLong,_ 'handle of bmp oldBmp as uLong 'returns previously selected bitmap open "Msimg32.dll" for DLL as #msimg CallDll #msimg, "TransparentBlt",_ hdc as ulong,_ 'The destination DC = graphicbox 30 as long,_ 'x location on destination 0 as long,_ 'y location on destination 250 as long,_ 'width to stretch to 300 as long,_ 'height to stretch to hMemDC as ulong,_ 'The source DC = memory 0 as long,_ 'x location in source 0 as long,_ 'y location in source 100 as long,_ 'width to take from source 90 as long,_ 'height to take from source 0 as ulong,_ 'RGB/long color value to make transparent result asbooleanlong 'nonzero if successful close #msimg wait [quit] calldll #gdi32, "DeleteDC",_ hMemDC as ulong,_ 'DC to delete re as long 'nonzero=success calldll #user32, "ReleaseDC",_ h as ulong,_ 'window handle hdc as ulong,_ 'device context ret as long close #1:end [[code]] =Demo Two= The second demo is identical to the first, with one important difference. We fill with an RGB color and specify that color as the transparent color in TransparentBlt. [[code format="lb"]] nomainwin winWide=700:winHigh=500 WindowWidth=winWide+50:WindowHeight=winHigh+50 UpperLeftX=1:UpperLeftY=1 graphicbox #1.g, 0,0,winWide,winHigh open "GDI Demo" for window as #1 #1 "trapclose [quit]" #1.g "down; fill 10 100 200; backcolor 10 100 200; color red" #1.g "font arial 20" #1.g "\\\Sample" 'capture a bitmap in memory with native commands #1.g "getbmp display 0 0 160 190" 'get handle for memory bmp handleBmp = hbmp("display") #1.g "fill yellow;flush" h=hwnd(#1.g) 'graphicbox handle 'get device context for window: calldll #user32, "GetDC",_ h as ulong,_ 'graphicbox handle hdc as ulong 'returns handle to device context calldll #gdi32, "CreateCompatibleDC",_ hdc as ulong,_ 'graphicbox DC hMemDC as ulong 'memory DC CallDLL #gdi32,"SelectObject",_ hMemDC as uLong,_ 'memory DC handleBmp as uLong,_ 'handle of bmp oldBmp as uLong 'returns previously selected bitmap lColor = (200*256*256) + (100*256) + 10 open "Msimg32.dll" for DLL as #msimg CallDll #msimg, "TransparentBlt",_ hdc as ulong,_ 'The destination DC = graphicbox 30 as long,_ 'x location on destination 0 as long,_ 'y location on destination 250 as long,_ 'width to stretch to 300 as long,_ 'height to stretch to hMemDC as ulong,_ 'The source DC = memory 0 as long,_ 'x location in source 0 as long,_ 'y location in source 100 as long,_ 'width to take from source 90 as long,_ 'height to take from source lColor as ulong,_ 'RGB/long color value to make transparent result asbooleanlong 'nonzero if successful close #msimg wait [quit] calldll #gdi32, "DeleteDC",_ hMemDC as ulong,_ 'DC to delete re as long 'nonzero=success calldll #user32, "ReleaseDC",_ h as ulong,_ 'window handle hdc as ulong,_ 'device context ret as long close #1:end [[code]] ---- [[GDI|GDI Tutorials Home]]