GDI+ DrawImage leaks memory but I don't know why

[funbotix]

I'm using Dev C++ to do a simple Win32 app on a Windows Embedded Standard platform and am having trouble understanding why this code has a memory leak. This is the WM_PAINT message handler for the window procedure. The 'initialized' variable is a global Boolean that's initialized to false, and then set true after the WM_CREATE message is handled.

case WM_PAINT:{
if(initialized){
PAINTSTRUCT ps;
hDC = BeginPaint(&ps);
static int slide = 0;
assert(slide >= 0);
assert(slide <= 28);
Image * pSlide = pSlides[slide];
Graphics graphics(hDC);
graphics.DrawImage(pSlide, 0, 0);
if(++slide > 28){
slide = 0;
}
}
break;
}

Prior to the WM_PAINT message being handled the pSlides[] array is globally declared and filled like this.

Image * pSlides[29];

case WM_CREATE:{
wchar_t filename[] = L"slides\\slide01.png";
for(int i=0; i<29; i++){
swprintf(filename,L"slides\\slide%02d.png", i);
pSlides[i] = new Image(filename);
assert(pSlides[i]);
}
initialized = true;
break;
}

Using Windows sysinternals process explorer, I can see that every time the WM_PAINT message draws an image (on top of the prior image) memory is leaked.

If I comment out the call to graphics.DrawImage, the memory leak goes away.

This slide show updates the screen once every second and runs for hours on end, until, I think, too much memory gets leaked at which point it appears to hang/crash.

Can anyone tell me how I can fix this memory leak?

Thanks!

[funbotix]

If I changed my graphics assets to use BMP instead of PNG files, so the DrawImage function is drawing Bitmaps instead of Images, the memory leak goes away. I don't see how or why that could be, but I did observe it.

Comments...?

[funbotix]

Now I'm really confused. I created my Bitmap objects like this

Bitmap * pSlide01 = new Bitmap(L"slides\\slide_01.bmp");
Bitmap * pSlide02 = new Bitmap(L"slides\\slide_02.bmp");
Bitmap * pSlide03 = new Bitmap(L"slides\\slide_03.bmp");
...
Bitmap * pSlide29 = new Bitmap(L"slides\\slide_29.bmp");
 

and drew them like this

switch(slide){
  case 1:  graphics.DrawImage(pSlide01,0,0); break;
  case 2:  graphics.DrawImage(pSlide02,0,0); break;
  case 3:  graphics.DrawImage(pSlide03,0,0); break;
  ...
  case 29: graphics.DrawImage(pSlide29,0,0); break;
}
 

and it works (no memory leaks). But... if I do this...

Bitmap * pSlides[29];
 
pSlides[0]  = pSlide01;
pSlides[1]  = pSlide02;
pSlides[2]  = pSlide03;
...
pSlides[28] = pSlide29;
 
graphics.DrawImage(pSlides[slide],0,0);
 

they're drawn properly but the memory leak comes back.

Any ideas why this might be?

Confuzed...

[weaknessforcats]

Your bitmaps are created on the heap using the new operator. Where is it you delete these allocations??

Deleting the array does not delete the elements.

[funbotix]

The bitmaps stay loaded for the duration of the app. They're for a slide show that repeats forever, until the app exits. Then they're deleted. They're loaded when the app window is created, and deleted with the app window is closed. They're not loaded over and over... they're only loaded once.

[funbotix]

I have another update... if I speed up the timer and change the slides 10 times per second, the memory leak occurs, but much more slowly, even if I do it without using the array of pointers to the bitmaps. However, if I comment out the call to DrawImage, the leak goes away forever.