Transferring Images with TransparentBlt

Janet Terra
Transferring Images with TransparentBlt | A Transparent Background for Static Graphics | The Demo Bitmaps | Demo 1: Drawbmp vs TransparentBlt | Demo 2: BitBlt, TransparentBlt and Drawing in Memory

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A Transparent Background for Static Graphics

Do you find yourself creating sprites, not for animation, but to draw static images with a transparent background? If you do, then consider using the API TransparentBlt function in MSIMG32.DLL. The MSIMG32.DLL is included with all versions of Window 98 and later. Sorry, Windows 95 Users, this doesn't include you , although you may be able to download the DLL. The TransparentBlt coding is very similar to the BitBlt and StretchBlt functions of GDI32.DLL. If you are unfamiliar with transferring bits using BitBlt, please read Bitmaps the Fast Way (Newsletter 122) by Callum Lowcay. This is an excellent article demonstrating how BitBlt works.

Finding, Opening and Closing the DLL

There is no need to include a separate MSIMG32.DLL file with programs calling this DLL if your operating system is Windows 98 or later. You will need to OPEN the DLL. Common Windows operating system DLL's do not need to be OPENed before calling. These common DLL's include USER32.DLL, KERNEL32.DLL, GDI32.DLL, WINMM.DLL, SHELL32.DLL, COMDLG32.DLL, COMCTL32.DLL. MSIMG32.DLL DOES REQUIRE OPENing before CALLing.

 open msimg32.dll for dll as #m 

As with all OPENed DLL's, the DLL must be closed before exiting the program.

 close #m 

BitBlt, StretchBlt, TransparentBlt: A Quick Comparison

Capabilities	BitBlt	TransparentBlt	StretchBlt
Simple bitcopy	Yes	Yes	Yes
Bitcopy from memory device	Yes	Yes	Yes
Resize	No	Yes	Yes
Raster Operations	Yes	No	Yes
Flip	No	No	Yes
Mirror	No	No	Yes
Rotate 180 degrees	No	No	Yes
Assign Color Transparent	No	Yes	No

The Demo Bitmaps

These two demos generate a simple image. You may choose to load an image from file with the loadbmp command. The demos are based upon the white background of the drawn image. If you choose to substitute with an image having a different background color, change the long number value of white (16777215) to the long number value of the desired color.

Demo 1: Drawbmp vs TransparentBlt

This first demo illustrates the difference between drawing an image with the drawbmp command and drawing the same image with the TransparentBlt API function.

 'Demo Drawing Bitmaps with Transparent Backgrounds 
 'Using msimg32.dll and TransparentBlt 
 'Copyright Janet Terra December 2004, 2011 
 'This information is free for anyone to use in your program 
 'but this demo itself may not be copied 'as is' and reposted 
 
 'Users of PRE WINDOWS 98, please note: 
 'The msimg32.dll may not be available for Windows 95 
 'If running this program gives you - Runtime Error: The 
 'specified module could not be found. (OS error 16r7E) 
 'then msimg32.dll is not present on your computer. 
 
 'In addition, memory leaks have been associated with 
 'repeated TransparentBlt calls and Windows 95/98 
 'Visit http://support.microsoft.com for more info 
 
 'Load a bitmap. This demo uses Star.bmp 
 
 open "Quick Pic" for graphics as #1 
 #1 "down; color red; backcolor yellow" 
 #1 "place 50 30; circlefilled 25" 
 #1 "getbmp pic 10 0 88 64" 
 close #1 
 
 nomainwin 
 WindowWidth = 420 
 WindowHeight = 420 
 
 'Define 6 Graphicboxes: 1,2,3 = Drawbmp, 4,5,6 = TransparentBlt 
 graphicbox #w.g1, 10, 10, 100, 100 
 statictext #w.stxt1a, "Drawbmp pic 0, 0", 8, 120, 110, 16 
 statictext #w.stxt1b, "white background", 8, 136, 110, 16 
 graphicbox #w.g2, 140, 10, 100, 100 
 statictext #w.stxt2a, "Drawbmp pic 0, 0", 138, 120, 110, 16 
 statictext #w.stxt2b, "blue background", 138, 136, 110, 16 
 graphicbox #w.g3, 270, 10, 100, 100 
 statictext #w.stxt3a, "Drawbmp pic 0, 0", 268, 120, 110, 16 
 statictext #w.stxt3b, "patterned background", 268, 136, 110, 16 
 graphicbox #w.g4, 10, 190, 100, 100 
 statictext #w.stxt4a, "Using TransparentBlt", 8, 300, 110, 16 
 statictext #w.stxt4b, "white background", 8, 316, 110, 16 
 statictext #w.stxt4c, "same width and height", 8, 332, 110, 16 
 graphicbox #w.g5, 140, 190, 100, 100 
 statictext #w.stxt5a, "Using TransparentBlt", 138, 300, 110, 16 
 statictext #w.stxt5b, "blue background", 138, 316, 110, 16 
 statictext #w.stxt5c, "smaller width and height (shrink)", 138, 332, 110, 32 
 graphicbox #w.g6, 270, 190, 100, 100 
 statictext #w.stxt6a, "Using TransparentBlt", 268, 300, 110, 16 
 statictext #w.stxt6b, "patterned background", 268, 316, 110, 16 
 statictext #w.stxt5c, "larger width and height (stretch)", 268, 332, 110, 32 
 
 
 'Open the Window 
 open "Demo #1" for window as #w 
 #w "trapclose [endProgram]" 
 
 'Obtain the handles of the primary window, the source window or graphicbox, 
 'and the destination windows or graphicboxes. In this demo, the first graphicbox 
 '(the bitmap drawn against a white background) also serves as the source bitmap) 
 
 hW = hWnd(#w) 'Window handle 
 hWG1 = hWnd(#w.g1) 'Source Handle 
 hWG4 = hWnd(#w.g4) 'Destination Handle (#w.g4) 
 hWG5 = hWnd(#w.g5) 'Destination Handle (#w.g5) 
 hWG6 = hWnd(#w.g6) 'Destination Handle (#w.g6) 
 hDC1 = GetDC(hWG1) 'Source Device Control Context 
 hDC4 = GetDC(hWG4) 'Destination Device Context (#w.g4) 
 hDC5 = GetDC(hWG5) 'Destination Device Context (#w.g5) 
 hDC6 = GetDC(hWG6) 'Destination Device Context (#w.g6) 
 
 'Open the msimg32.dll 
 Open "msimg32.dll" for DLL as #m 
 
 'Display White, Blue and Patterned Backgrounds 
 call hueBackground "white", "#w.g1" 
 call hueBackground "darkblue", "#w.g2" 
 call patternedBackground "#w.g3" 
 call hueBackground "white", "#w.g4" 
 call hueBackground "darkblue", "#w.g5" 
 call patternedBackground "#w.g6" 
 
 'Draw the bitmap in the first graphicbox. Remember this also serves as the 
 'source bitmap. 
 #w.g1 "drawbmp pic 0, 0" 
 
 'Draw the bitmap in the second graphicbox. The white rectangular background 
 'of the pic remains present 
 #w.g2 "drawbmp pic 0, 0" 
 
 'Draw the bitmap in the third graphicbox. Again, the white rectangular 
 'background of the bitmap obscures the patterned background 
 #w.g3 "drawbmp pic 0, 0" 
 
 'Assign ONE color to be the transparent color. Remember you must use the 
 'long number. In this case, the RGB of White is "255 255 255", so the 
 'long number is 255 + 255*256 + 255*256*256 or 16777215 
 transpColor = 16777215 
 
 'Function variables are (DestinationDC, DestinationUpperLeftX, DestinationUpperLeftY, 
 'DestinationWidth, DestinationHeight, SourceDC, SourceUpperLeftX, 
 'SourceUpperLeftY, SourceWidth, SourceHeight, TransparentColor) 
 
 'Using the SAME Width and Height as the Source 
 null = TransparentBlt(hDC4, 0, 0, 88, 64, hDC1, 0, 0, 88, 64, 16777215) 
 
 'Using a SMALLER Width and Height as the Source 
 null = TransparentBlt(hDC5, 0, 0, 44, 32, hDC1, 0, 0, 88, 64, 16777215) 
 
 'Using a LARGER Width and Height as the Source (Destination x and y are also changed) 
 null = TransparentBlt(hDC6, 0, 0, 104, 80, hDC1, 0, 0, 88, 64, 16777215) 
 
 Wait 
 
 [endProgram] 
 'Release memory from any device contexts created during program 
 null = ReleaseDC(hWG1, hDC1) 
 null = ReleaseDC(hWG4, hDC4) 
 null = ReleaseDC(hWG5, hDC5) 
 null = ReleaseDC(hWG6, hDC6) 
 'Close msimg32.dll 
 close #m 
 'Unload bitmap 
 unloadbmp "pic" 
 'Close window 
 close #w 
 'End program 
 end 
 
 sub hueBackground hue$, handle$ 
 #handle$ "down; fill ";hue$ 
 #handle$ "flush; discard" 
 end sub 
 
 sub patternedBackground handle$ 
 colorStrand$ = "yellow blue darkgreen darkblue darkpink" 
 colorCode = 0 
 #handle$, "down" 
 for ii = 1 to 100 
 colorCode = colorCode + 1 
 if colorCode = 6 then 
 colorCode = 1 
 end if 
 colorCode$ = word$(colorStrand$, colorCode) 
 #handle$ "color ";colorCode$ 
 #handle$ "line ";ii;" 0 ";ii;" 100" 
 next ii 
 #handle$ "flush; discard" 
 end sub 
 
 '==================================================================== 
 'These 3 Functions obtained from information found in API's for 
 'Liberty BASIC (c) Alyce Watson and used with permission of Alyce Watson 
 '==================================================================== 
 
 function TransparentBlt(hdcDest, xDest, yDest, wDest, hDest, hdcSource, xSource, ySource, wSource, hSource, clrTransp) 
 calldll #m, "TransparentBlt", _ 
 hdcDest as ulong, _ 'handle to destination DC 
 xDest as long, _ 'x-coord of destination upper-left corner 
 yDest as long, _ 'y-coord of destination upper-left corner 
 wDest as long, _ 'width of destination rectangle 
 hDest as long, _ 'height of destination rectangle 
 hdcSource as ulong, _ 'handle to source DC 
 xSource as long, _ 'x-coord of source upper-left corner 
 ySource as long, _ 'y-coord of source upper-left corner 
 wSource as long, _ 'width of source rectangle 
 hSource as long, _ 'height of source rectangle 
 clrTransp as ulong, _ 'color to make transparent 
 TransparentBlt as long 
 end function 
 
 function GetDC(handle) 
 calldll #user32, "GetDC", _ 
 handle as ulong, _ 
 GetDC as ulong 
 end Function 
 
 function ReleaseDC(handle, hdc) 
 calldll #user32, "ReleaseDC", _ 
 handle as ulong, _ 
 hdc as ulong, _ 
 ReleaseDC as ulong 
 end Function 
 '==================================================================== 

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You may choose to select any image. If you do, it is important to note that TransparentBLT will fail unless the width and height values of the bitmap in memory correspond with the file width and height values of that bitmap.

In this line

 null = TransparentBlt(hDC2, 0, 0, 57, 57, 44, 32, hDCM, 0, 0, 57, 57, 88, 64, 16777215) 

If your bitmap is 48 pixels wide by 60 pixels long and you want to shrink it to 24 pixels wide by 30 pixels long, then change the above line to

 null = TransparentBlt(hDC2, 0, 0, 57, 57, 24, 30, hDCM, 0, 0, 48, 60, 16777215) 

TransparentBlt is best used for transferring images using a transparent background. Although TransparentBlt is documented to resize images, at least one user with Windows 7 has found the resizing function to fail when transferring from one graphicbox to another. The function did succeed when the image was transferred from a memory dc to a graphicbox. It is best to transfer the image from a memory device context as dexcribed in the next demo.

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Demo 2: BitBlt, TransparentBlt and Drawing in Memory

If you haven't done so already, please read Drawing IN MEMORY (Newsletter 101) by Alyce Watson . There you'll find all the theory you need to understand that you can transfer an image drawn in memory but you can't transfer an image drawn in a hidden graphic box. This second demo demonstrates how to load a bitmap and then transferring that image to a graphicbox using both BitBlt and TransparentBlt.

 'Demo Transferring an Image from a Bitmap Loaded in Memory 
 'Using gdi32.dll: BitBlt and msimg32.dll: TransparentBlt 
 'Copyright Janet Terra December 2004, 2011 
 'This information is free for anyone to use in your program 
 'but this demo itself may not be copied 'as is' and reposted 
 
 'Users of PRE WINDOWS 98, please note: 
 'The msimg32.dll may not be available for Windows 95 
 'If running this program gives you - Runtime Error: The 
 'specified module could not be found. (OS error 16r7E) 
 'then msimg32.dll is not present on your computer. 
 
 
 nomainwin 
 
 'Load a bitmap. This demo gets a bitmap 88 x 64 so no external 
 'files are needed 
 
 WindowWidth = 280 
 WindowHeight = 400 
 
 open "Quick Pic" for graphics as #1 
 #1 "down; color red; backcolor yellow" 
 #1 "place 50 30; circlefilled 25" 
 #1 "getbmp pic 10 0 88 64" 
 close #1 
 
 
 'Define 2 Graphicboxes: 1 = BitBlt, 2 = TransparentBlt 
 graphicbox #w.g1, 10, 10, 100, 100 
 statictext #w.st1a, "Image transferred from memory using", 8, 120, 110, 32 
 statictext #w.st1b, "gdi32.dll", 8, 152, 110, 16 
 statictext #w.st1c, "BitBlt", 8, 168, 110, 16 
 graphicbox #w.g2, 140, 10, 100, 100 
 statictext #w.st2a, "Image transferred from memory using", 138, 120, 110, 32 
 statictext #w.st2b, "msimg32.dll", 138, 152, 110, 16 
 statictext #w.st2c, "TransparentBlt", 138, 168, 110, 16 
 
 
 'Open the Window 
 open "Demo" for window as #w 
 #w "trapclose [endProgram]" 
 
 'Obtain the handles of the primary window, the source window or graphicbox, 
 'and the destination windows or graphicboxes. In this demo, #w.g1 receives the 
 'image using BitBlt and #w.g2 receives the image using TransparentBlt 
 
 hW = hWnd(#w) 'Window handle 
 hWG1 = hWnd(#w.g1) 'Source Handle (#w.g1) 
 hWG2 = hWnd(#w.g2) 'Destination Handle (#w.g2) 
 hDC = GetDC(hW) 
 hDC1 = GetDC(hWG1) 'Source Device Context (#w.g1) 
 hDC2 = GetDC(hWG2) 'Destination Device Context (#w.g2) 
 
 'Open the msimg32.dll 
 open "msimg32.dll" for dll as #m 
 
 'Create Device Context in Memory 
 hDCM = CreateCompatibleDC(0) 
 
 'Obtain Handle of the Loaded BMP ("pic") 
 hPic = hBmp("pic") 
 
 'Display Solid Backgrounds 
 call hueBackground "Darkblue", "#w.g1" 
 call hueBackground "Darkblue", "#w.g2" 
 
 'Select the Object in Memory 
 memPic = SelectObject(hDCM, hPic) 
 
 'Draw the Object in Memory to GraphicBox #w.g1 using BitBlt 
 null =BitBlt(hDC1, 0, 0, 88, 64, hDCM, 0, 0, _SRCCOPY) 
 
 'Draw the Object in Memory to GraphicBox #w.g2 using TransparentBlt 
 null = TransparentBlt(hDC2, 0, 0, 88, 64, hDCM, 0, 0, 88, 64, 16777215) 
 
 wait 
 
 [endProgram] 
 'Release memory from any device contexts created during program 
 null = ReleaseDC(hWG1, hDC1) 
 null = ReleaseDC(hWG2, hDC2) 
 calldll #gdi32, "DeleteDC", _ 
 hDCM as ulong, _ 
 null as long 
 
 calldll #gdi32, "DeleteObject", _ 
 memPic as ulong, _ 
 null as long 
 
 'Close msimg32.dll 
 close #m 
 'Unload bitmap 
 unloadbmp "pic" 
 'Close window 
 close #w 
 'End program 
 end 
 
 sub hueBackground hue$, handle$ 
 #handle$ "down; fill ";hue$ 
 #handle$ "flush; discard" 
 end sub 
 
 '==================================================================== 
 'The following functions are derived from information obtained from 
 'API's for Liberty BASIC (c) Alyce Watson and are used with permission 
 'of Alyce Watson 
 '==================================================================== 
 
 function CreateCompatibleDC(hDC) 
 calldll #gdi32, "CreateCompatibleDC", _ 
 hDC as ulong, _ 'current screen 
 CreateCompatibleDC as ulong 'handle of memory DC 
 end function 
 
 function GetDC(handle) 
 calldll #user32, "GetDC", _ 
 handle as ulong, _ 
 GetDC as ulong 
 end function 
 
 function ReleaseDC(handle, hdc) 
 calldll #user32, "ReleaseDC", _ 
 handle as ulong, _ 
 hdc as ulong, _ 
 ReleaseDC as ulong 
 end function 
 
 function SelectObject(hDC,hImage) 
 calldll #gdi32, "SelectObject", _ 
 hDC as ulong, _ 'Memory Device Context 
 hImage as ulong, _ 'Handle of Loaded Bitmap 
 SelectObject as ulong 'Returns handle of previous object 
 end function 
 
 function BitBlt(hdcDest, xDest, yDest, wDest, hDest, hdcSource, xSource, ySource, ROP) 
 CallDLL #gdi32, "BitBlt", _ 
 hdcDest as ulong, _ 'handle to destination DC 
 xDest as long, _ 'x-coord of destination upper-left corner 
 yDest as long, _ 'y-coord of destination upper-left corner 
 wDest as long, _ 'width of destination rectangle 
 hDest as long,_ 'height of destination rectangle 
 hdcSource as ulong, _ 'handle to source DC 
 xSource as long, _ 'x-coord of source upper-left corner 
 ySource as long, _ 'y-coord of source upper-left corner 
 ROP as ulong,_ 'Raster Operation 
 result as long 
 end function 
 
 function TransparentBlt(hdcDest, xDest, yDest, wDest, hDest, hdcSource, xSource, ySource, wSource, hSource, clrTransp) 
 calldll #m, "TransparentBlt", _ 
 hdcDest as ulong, _ 'handle to destination DC 
 xDest as long, _ 'x-coord of destination upper-left corner 
 yDest as long, _ 'y-coord of destination upper-left corner 
 wDest as long, _ 'width of destination rectangle 
 hDest as long, _ 'height of destination rectangle 
 hdcSource as ulong, _ 'handle to source DC 
 xSource as long, _ 'x-coord of source upper-left corner 
 ySource as long, _ 'y-coord of source upper-left corner 
 wSource as long, _ 'width of source rectangle 
 hSource as long, _ 'height of source rectangle 
 clrTransp as ulong, _ 'color to make transparent 
 TransparentBlt as long 
 end function 
 '==================================================================== 

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Transferring Images with TransparentBlt | A Transparent Background for Static Graphics | The Demo Bitmaps | Demo 1: Drawbmp vs TransparentBlt | Demo 2: BitBlt, TransparentBlt and Drawing in Memory