loading and displaying images

[candc32]

what library do I need to load .png's and .bmp's?

[taymo2020]

SDL alone will do BMP's and SDL_image will load PNG's along with a couple more. Althought they all load into SDL's SDL_Surface structure that might be unusable in your situation.

[Samuel]

For Bitmaps, you could use the windows function LoadImage(); or you could use the glaux library. I recommend LoadImage() because glaux has memory leaks.

[candc32]

For Bitmaps, you could use the windows function LoadImage(); or you could use the glaux library. I recommend LoadImage() because glaux has memory leaks.

so I do this?

Code: Select all

#include <windows>
using namespace std;

int main()
{
    loadimage("test.bmp");
}


[tomcant]

For Bitmaps, you could use the windows function LoadImage(); or you could use the glaux library. I recommend LoadImage() because glaux has memory leaks.

so I do this?

Code: Select all

#include <windows>
using namespace std;

int main()
{
    loadimage("test.bmp");
}


Heck no! Nothing is that simple with the WinAPI.

I put something together a while back that loads/displays more than just bitmap file formats. The following code loads and displays the file "pic.bmp" from the same directory as the executable. You can display most common file formats (gif, etc.), by simply changing the `const char* picture_file="...";' line in WndProc().

main.cpp
[syntax="cpp"]#include "picture.h"

LRESULT CALLBACK WndProc(HWND hwnd,UINT msg,WPARAM wParam,LPARAM lParam){
static LPPICTURE pic=0;
static HDC hdc;
static PAINTSTRUCT ps;
static const char* picture_file="pic.bmp";

switch(msg){
case WM_CREATE:
pic=LoadPictureFile(picture_file);
break;

case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);

if(pic){
long hmWidth,hmHeight;
pic->get_Width(&hmWidth);
pic->get_Height(&hmHeight);

int nWidth=MulDiv(hmWidth,GetDeviceCaps(hdc,LOGPIXELSX),2540),
nHeight=MulDiv(hmHeight,GetDeviceCaps(hdc,LOGPIXELSY),2540);

RECT rc;
GetClientRect(hwnd,&rc);

pic->Render(hdc,0,0,nWidth,nHeight,0,hmHeight,hmWidth,-hmHeight,&rc);
}

EndPaint(hwnd,&ps);
break;

case WM_DESTROY:
PostQuitMessage(0);
break;

default:
return DefWindowProc(hwnd, msg, wParam, lParam);
} return 0;
}

int WINAPI WinMain(HINSTANCE hInst,HINSTANCE hPrev,LPSTR args,int nShow){
MSG msg;
WNDCLASS wc={0};
wc.lpszClassName="Win32App";
wc.hInstance=hInst;
wc.hbrBackground=GetSysColorBrush(COLOR_3DFACE);
wc.lpfnWndProc=WndProc;
wc.hCursor=LoadCursor(0,IDC_ARROW);

RegisterClass(&wc);

CreateWindow(wc.lpszClassName,"Image Loader",WS_OVERLAPPEDWINDOW|
WS_VISIBLE,CW_USEDEFAULT,CW_USEDEFAULT,400,400,0,0,hInst,0);

while(GetMessage(&msg,0,0,0)){
TranslateMessage(&msg);
DispatchMessage(&msg);
}

return (int)msg.wParam;
}[/syntax]

picture.h
[syntax="cpp"]#ifndef _PICTURE_H_
#define _PICTURE_H_

#include <windows.h>
#include <olectl.h>
#include <crtdbg.h>

LPPICTURE LoadPictureFile(LPCTSTR);

#endif[/syntax]

picture.cpp
[syntax="cpp"]#include "picture.h"

LPPICTURE LoadPictureFile(LPCTSTR szFile){
HANDLE hFile=CreateFile(szFile,GENERIC_READ,0,0,OPEN_EXISTING,0,0);

DWORD dwFileSize=GetFileSize(hFile,0);

LPVOID pvData=0;
HGLOBAL hGlobal=GlobalAlloc(GMEM_MOVEABLE,dwFileSize);

pvData=GlobalLock(hGlobal);

DWORD dwBytesRead=0;
BOOL bRead=ReadFile(hFile,pvData,dwFileSize,&dwBytesRead,0);
GlobalUnlock(hGlobal);
CloseHandle(hFile);

LPSTREAM pstm=0;
HRESULT hr=CreateStreamOnHGlobal(hGlobal,1,&pstm);

LPPICTURE pic;
hr=OleLoadPicture(pstm,dwFileSize,0,IID_IPicture,(LPVOID*)&pic);
pstm->Release();

return pic;
}[/syntax]

I havn't tested this for a while, but I think it worked the last time I checked. If you have any problems compiling the code, then post back here. Good luck!

[candc32]

it said no file called picture.h

[TheKidder]

Make sure the file called picture.h (the one above picture.cpp in tomcant's post) is in the same directory as picture.h and main.cpp

[candc32]

now its saying no file called crtdbg.h

[taymo2020]

Just curious, what API are you using for graphics?

[candc32]

whats API stand for?

[MXP]

Application Programming Interface

Taylor, it's OLE (Object Linking and Embedding... more or less COM). His method is a bit more powerful than LoadImage() but also worlds more complicated. I would personally just use LoadImage() and store everything as bitmaps. If I wanted PNGs then I'd get libpng.

[candc32]

well can some one give me an example of loadiamge()

[MXP]

This uses LoadBitmap() instead, but it's probably going to be more to you. You can replace any call to LoadBitmap() in that tutorial with a call to LoadImage().

[Dante Shamest]

LoadImage is a Windows API function. Unless you're planning to draw a bitmap onto a window (and assuming you know how to create a window), it's probably not suitable for your needs.

What do you wish to display the bitmap on? A console window? An overlapped window? Or do you just wish to get information about the bitmap?

The following code will load a bitmap named "bitmap.bmp" in the same directory as the program and print the bitmap's width and height.

[syntax="cpp"]#include <windows.h>
#include <cstdio>

int main()
{
// Load the bitmap file, bitmap.bmp and get a handle to it.
HBITMAP hBitmap = (HBITMAP) LoadImage( GetModuleHandle(NULL),
"bitmap.bmp",
IMAGE_BITMAP,
0,
0,
LR_LOADFROMFILE );

// Get information about the bitmap.
BITMAP bitmap = { 0 };
GetObject( hBitmap, sizeof(BITMAP), &bitmap ) ;

// Print information about the bitmap.
printf( "Bitmap width = %d\n", bitmap.bmWidth ) ;
printf( "Bitmap height = %d\n", bitmap.bmHeight ) ;

// Prevent windows console from closing immediately.
getchar() ;

return 0 ;
}[/syntax]

If you want to learn windows programming, check out the sticky in the windows programming forum. However you should already have a good grasp of C or C++.

[candc32]

ok what I want is to make a game like a little adventure zelda thing