WxImage

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[edit] wxImage

See also:

[edit] Gotcha's

If you're opening a file and get: 'Warning: No image handler for type xx defined.', you probably forgot to add the image handler and/or initialise all handlers. See wxImage and wxImageHandler.

The default compression algorithm for the TIFF image handler's SaveFile method is LZW. This algorithm is patented by Unisys Corporation. Unisys is currently enforcing its patent, so software which uses LZW may be held liable. For more information see http://www.unisys.com/about__unisys/lzw. In particular, this patent is no longer enforceable in Canada, France, Germany, Italy, Japan, the United Kingdom and the United States of America - but it remains enforceable in other countries.

[edit] wxBasic implementation

This short example shows how to use wxImage to resize an image. 


 dim Path_img = "immagine.bmp" '     ******* CHANGE NAME HERE!!! ******
 
 frame = new wxFrame( Null, -1, "Using wxImage",wxPoint(20,20),wxSize(320,200+25))
 panel = new wxPanel( frame, -1 ,wxPoint(0,200),wxSize(320,200))
 panel2= new wxPanel( frame,-1,wxPoint(-1,-1),wxSize(0,0))
 
 bmp  = new wxEmptyImage(0,0)  ' Create an empty Image. Size does NOT matter...
 img = new wxEmptyBitmap(0,0) 'Create empty bitmap
 
 bmp2DC = wxMemoryDC()   ' Allocate memory: this space will be used to store the bitmap.
 
 if(bmp.LoadFile(Path_img, wxBITMAP_TYPE_BMP)) then   'Load image
     wxMessageBox("image loaded correctly")
 end if
 
 'resize l'immagine
     wxMessageBox("Original size(X,Y) = (" & bmp.GetWidth() & "," & bmp.GetHeight() & ")")    
     bmp = bmp.Scale(60,60) ' Change image size
     wxMessageBox("Size(X,Y) after resize = (" & bmp.GetWidth() & "," & bmp.GetHeight() & ")")
 
     bmp2 = bmp.ConvertToBitmap()    'convert image into bmp
     wxMessageBox("convert image into bitmap")
 
 
 
 Sub onPaint( event )
     dc = wxPaintDC( frame )
     dc.BeginDrawing()
         dc.DrawBitmap(bmp2,1,1,FALSE) 'draw converted image
     dc.EndDrawing()
 End Sub
 
 Connect( frame, -1, wxEVT_PAINT, "onPaint" )
 
 frame.Show(True)


You can find wxBasic at this address. The language is under development, so the above source may require minor adjustement on some wxBasic versions.

[edit] Creating Standalone Copy of wxImage

The wxImage copy constructor doesn't seem to create a new copy of the image object. I used this code to do so: 

wxImage * m_pOldImg = new wxImage( "image.bmp", wxBITMAP_TYPE_BMP, -1 );

int dataSize = m_pOldImg->GetWidth( )*m_pOldImg->GetHeight( )*3;
unsigned char * NewImgData = ( unsigned char * ) malloc( dataSize );
unsigned char * OldImgData = m_pOldImg->GetData( );

memcpy( NewImgData, OldImgData, dataSize );

wxImage * m_pNewImg = new wxImage( m_pOldImg->GetWidth( ), m_pOldImg->GetHeight( ), NewImgData );

A neater way would be to use wxImage::Copy, but at the time of writing (jan 2006), you need to copy the Alpha channel manually (GetAlphaData(), memcpy, SetAlphaData()).

[edit] Supported image formats

I have the following code snippet in an app to find out what image formats are available for use: 

#include <wx/list.h>

WX_DECLARE_LIST(wxImageHandler, HandlerList);
#include <wx/listimpl.cpp>
WX_DEFINE_LIST(HandlerList);

wxChoice *formatchoice = new wxChoice( this, -1 );
wxImageHandler* handler;

wxInitAllImageHandlers();

HandlerList& handlers = (HandlerList&)wxImage::GetHandlers();
HandlerList::Node *node = handlers.GetFirst();

while(node) {
  wxString extn;
  handler = (wxImageHandler *)node->GetData();
  extn = handler->GetExtension();
  if(extn.Len() > 0) formatchoice->Append(handler->GetExtension(), (void *)handler);

/* If you want to use this for saving, add these checks to the if statement. */

/* && extn != "cur" // Format not good for general-purpose writing
   && extn != "ico" // Format not good for general-purpose writing
   && extn != "iff" // wx Doesn't support writing to this
   && extn != "gif" // wx Doesn't support writing to this
   && extn != "ani"  // wx Doesn't support writing to this
*/

  node = node->GetNext();
}

/* Use the wxChoice however you want */

const wxString mimetype = ((wxImageHandler *)formatchoice->GetClientData(formatchoice->GetSelection()))->GetMimeType();
if(image.SaveFile(filename->GetValue(), mimetype ) == TRUE) {
  /* Image saved successfully */
} else {
  /* Image not saved successfully */
}

[edit] Correct SetData Documentation

The docs don't correctly document the SetData method. The actual methods for SetImage are: 

   void SetData( unsigned char *data, bool static_data=false );
   void SetData( unsigned char *data, int new_width, int new_height, bool static_data=false );

The most important part is the "static_data" parameter. If you pass true, then wxImage will not try to free the memory. It's also important to note that if you pass "false", thereby indicating that you wish wxImage to delete the data in its own destructor that the memory used for the data was allocated with "malloc()" (i.e. NOT "new" or "new <type>[]) as wxImage's destructor will destroy the data with "free()"

Retrieved from "http://wiki.wxwidgets.org/WxImage"
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