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Intermediate
Display PNG, JPG, etc on PocketPCBy Jim KoornneefCombine CXImage and DibSectionLite on PocketPC |
VC6, VC7, Windows, PocketPC 2002, MFC, Dev
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I found some very good and useful code out there in CodeProject and was able to combine them (with some modifications and enhancements) into group of very useful libraries.
I won't go into too many details, as I've basically taken Chris Maunder's DibSectionLite and added methods to load using Davide Pizzolato's CXImage classes. You can find their original libraries and documentation on this site. No point in replicating it here.
#define changes and #ifdef out any try...catch code. I opted to return
false.
The next step was debugging the PNG code. Since the PNG library uses function pointers, it turns out that eVC modifies the signature between a debug and release build. The stack becomes corrupt upon return unless the signature for these functions are modified as below:
#if defined (_WIN32_WCE) && !defined (_DEBUG) #define _CDECL_MODE_ __cdecl #else #define _CDECL_MODE_ #endif static void _CDECL_MODE_ user_write_data(png_structp png_ptr, png_bytep data, png_size_t length)Finally, I modified DibSectionLite to include:
Load and Save now take a CFile or CString.. Useful for memory images
(CMemFile)CXImage.
You can add support and shrink/expand you executable size based on these defines as well as the ones in
CXImage:
#define DIBSECTION_SUPPORT_BMP 1 #define DIBSECTION_SUPPORT_GIF 1 // Patented! #define DIBSECTION_SUPPORT_JPG 1 #define DIBSECTION_SUPPORT_PNG 1 //#define DIBSECTION_SUPPORT_MNG 0 // Orig. Lib disabled this #define DIBSECTION_SUPPORT_ICO 1 //#define DIBSECTION_SUPPORT_TIF 0 // Patented! //too many problems with // __cdecl, see header //jk #define DIBSECTION_SUPPORT_TGA 1 #define DIBSECTION_SUPPORT_PCX 1 //#define DIBSECTION_SUPPORT_WBMP 0 //totally corrupt image... This might // take some work. //jk //#define DIBSECTION_SUPPORT_WMF 0 // WMF and PocketPC don't go hand-in hand // too well (GetEnhMetaFilePaletteEntries // unsupported by the OS). //#define DIBSECTION_SUPPORT_J2K 0 // Beta //totally corrupt image... This //might take some work. //jk #define DIBSECTION_SUPPORT_JBG 1 // Patented! see ../jbig/patents.htm
BOOL LoadPNG(LPCTSTR lpszFileName); BOOL LoadJPG(LPCTSTR lpszFileName); BOOL LoadBMP(LPCTSTR lpszFileName); BOOL LoadGIF(LPCTSTR lpszFileName); BOOL LoadMNG(LPCTSTR lpszFileName); BOOL LoadICO(LPCTSTR lpszFileName); BOOL LoadTIF(LPCTSTR lpszFileName); BOOL LoadTGA(LPCTSTR lpszFileName); BOOL LoadPCX(LPCTSTR lpszFileName); BOOL LoadWBMP(LPCTSTR lpszFileName); BOOL LoadWMF(LPCTSTR lpszFileName); BOOL LoadJ2K(LPCTSTR lpszFileName); BOOL LoadJBG(LPCTSTR lpszFileName);The code unravels and builds as a bunch of .LIB
You can compile and build the PocketPCTest app for your device. It is nothing fancy. Simply an exerciser. Uncomment the line in PocketPCTestView.cpp as needed.
The test app includes a definition of:
CDIBSectionLite m_image;in the header.
To Draw:
void CPocketPCTestView::OnDraw(CDC* pDC) { CPocketPCTestDoc* pDoc = GetDocument(); ASSERT_VALID(pDoc); // TODO: add draw code for native data here m_image.Draw(pDC, CPoint(0,0)); }And to load:
CPocketPCTestView::CPocketPCTestView()
{
// TODO: add construction code here
m_image.LoadPNG(_T("\\test.png")); // 24bit OK
// m_image.LoadPNG(_T("\\test-pal.png")); // 256 OK
// m_image.LoadJPG(_T("\\test.JPG")); //ok
// m_image.LoadBMP(_T("\\test.BMP")); //ok
// m_image.LoadGIF(_T("\\test.GIF")); //ok
// m_image.LoadICO(_T("\\test.ICO")); //ok
// m_image.LoadTGA(_T("\\test.TGA")); //ok
// m_image.LoadPCX(_T("\\test.PCX")); //ok
// m_image.LoadJBG(_T("\\test.JBG")); //ok
// This wasn't in the original code.
//// m_image.LoadMNG(_T("\\test.MNG"));
// WMF and PocketPC don't go hand-in hand too well (GetEnhMetaFilePaletteEntries
// unsupported by the OS).
//// m_image.LoadWMF(_T("\\test.WMF"));
// too many problems with __cdecl, see header
//// m_image.LoadTIF(_T("\\test.TIF"));
// totally corrupt image... This might take some work.
//// m_image.LoadWBMP(_T("\\test.WBMP"));
// totally corrupt image... This might take some work.
//// m_image.LoadJ2K(_T("\\test.J2K"));
}
That's about it. I didn't really spend much time with making J2K, TIF, and WBMP work. I'll update the article if someone gets them working.
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Last Updated: 22 Sep 2002 Editor: Chris Maunder |
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