win32 C++ put an image on the screen - c++

Question

i am learning C++ but i am having problems with putting an image on the screen.
i have searched the internet for help but i couldn't find any.
i am trying to create a window and put a simple color in the client area when the WM_Paint message is called, but the program just displays a grey screen as usual. i am using code::blocks 10.05.
#include <windows.h>
#include <iostream>
using namespace std;
int winx = 500;
int winy = 500;
int winbpp = 24;
static char m_bibuf[ sizeof(BITMAPINFOHEADER) + 12 ];
static BITMAPINFO &m_bi = *(BITMAPINFO*)&m_bibuf;
static BITMAPINFOHEADER &m_bih = m_bi.bmiHeader;
int* buffer = new int[winx*winy*winbpp];
int setbuffer()
{
for(int x = 0; x < winx; x++)
{
for(int y=0; y < winy; y++)
{
for(int z =0; z < winbpp; z++)
{
buffer[x*y*z] = 1;
}
}
}
return 0;
}
/* Declare Windows procedure */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
/* Make the class name into a global variable */
char szClassName[ ] = "CodeBlocksWindowsApp";
int WINAPI WinMain (HINSTANCE hThisInstance,
HINSTANCE hPrevInstance,
LPSTR lpszArgument,
int nCmdShow)
{
HWND hwnd; /* This is the handle for our window */
MSG messages; /* Here messages to the application are saved */
WNDCLASSEX wincl; /* Data structure for the windowclass */
/* The Window structure */
wincl.hInstance = hThisInstance;
wincl.lpszClassName = szClassName;
wincl.lpfnWndProc = WindowProcedure; /* This function is called by windows */
wincl.style = CS_DBLCLKS; /* Catch double-clicks */
wincl.cbSize = sizeof (WNDCLASSEX);
/* Use default icon and mouse-pointer */
wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName = NULL; /* No menu */
wincl.cbClsExtra = 0; /* No extra bytes after the window class */
wincl.cbWndExtra = 0; /* structure or the window instance */
/* Use Windows's default colour as the background of the window */
wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;
/* Register the window class, and if it fails quit the program */
if (!RegisterClassEx (&wincl))
return 0;
/* The class is registered, let's create the program*/
hwnd = CreateWindowEx (
0, /* Extended possibilites for variation */
szClassName, /* Classname */
" project 1 ", /* Title Text */
WS_OVERLAPPEDWINDOW, /* default window */
CW_USEDEFAULT, /* Windows decides the position */
CW_USEDEFAULT, /* where the window ends up on the screen */
winx, /* The programs width */
winy, /* and height in pixels */
HWND_DESKTOP, /* The window is a child-window to desktop */
NULL, /* No menu */
hThisInstance, /* Program Instance handler */
NULL /* No Window Creation data */
);
/* Make the window visible on the screen */
ShowWindow (hwnd, nCmdShow);
/* Run the message loop. It will run until GetMessage() returns 0 */
while (GetMessage (&messages, NULL, 0, 0))
{
/* Translate virtual-key messages into character messages */
TranslateMessage(&messages);
/* Send message to WindowProcedure */
DispatchMessage(&messages);
}
/* The program return-value is 0 - The value that PostQuitMessage() gave */
return messages.wParam;
}
/* This function is called by the Windows function DispatchMessage() */
LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message) /* handle the messages */
{
case WM_CREATE:
{
m_bih.biWidth = winx;
m_bih.biHeight = winy;
m_bih.biBitCount = winbpp;
m_bih.biSize = sizeof(m_bih);
m_bih.biPlanes = 1; // DIBs are upside down
m_bih.biCompression = BI_BITFIELDS;
m_bih.biSizeImage = 0;
m_bih.biXPelsPerMeter = 0;
m_bih.biYPelsPerMeter = 0;
m_bih.biClrUsed = 0;
m_bih.biClrImportant = 0;
setbuffer();
InvalidateRect(hwnd, NULL, TRUE);
} break;
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hDC = BeginPaint(hwnd, &ps);
RECT client;
GetClientRect(hwnd, &client);
StretchDIBits ( hDC,
0, // Destination top left hand
// corner X Position
0, // Destination top left hand
// corner Y Position
client.right, // Destinations width
client.bottom, // Destinations height
0, // Source top left hand
// corner's X Position
0, // Source top left hand
// corner's Y Position
winx, // Sources width
winy, // Sources height
buffer, // Source's data
&m_bi, // Bitmap Info
DIB_RGB_COLORS, // operations
SRCCOPY);
EndPaint(hwnd, &ps);
} break;
case WM_DESTROY:
delete buffer;
PostQuitMessage (0); /* send a WM_QUIT to the message queue */
break;
default: /* for messages that we don't deal with */
return DefWindowProc (hwnd, message, wParam, lParam);
}
return 0;
}
the program compiles normally, but instead of displaying the contents of 'buffer' in the client area,
it just displays the grey color like usual.
is 'buffer' formatted correctly?
=updated code below=
#include <windows.h>
int winx = 500;
int winy = 400;
int bpp = 24;
size_t pwidth;
int scanlinewidth = 0;
int numscanlines = 0;
bool setscanline = 1;
bool setbitmap = 1;
BITMAPINFO m_bi;
struct BGR{ char blue; char green; char red;};
BGR* buffer;
void setframebuffer()
{
m_bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
m_bi.bmiHeader.biPlanes = 1;
m_bi.bmiHeader.biBitCount = bpp;
m_bi.bmiHeader.biCompression = BI_RGB;
m_bi.bmiHeader.biSizeImage = 0;
m_bi.bmiHeader.biXPelsPerMeter = 100;
m_bi.bmiHeader.biYPelsPerMeter = 100;
m_bi.bmiHeader.biClrUsed = 0;
m_bi.bmiHeader.biClrImportant = 0;
if (setbitmap)
{
m_bi.bmiHeader.biWidth = scanlinewidth;
m_bi.bmiHeader.biHeight = numscanlines;
setbitmap = 0;
}
if (!setbitmap)
{
pwidth = (scanlinewidth * 3 + 3) & ~3;
buffer = new BGR[(scanlinewidth + pwidth)*numscanlines];
}
for (int i = 0; i < ((scanlinewidth + pwidth) * numscanlines); i++)
{
buffer[i].blue = 0;
buffer[i].green = 0;
buffer[i].red = 255;
}
}
/* Declare Windows procedure */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
/* Make the class name into a global variable */
char szClassName[ ] = "CodeBlocksWindowsApp";
int WINAPI WinMain (HINSTANCE hThisInstance,
HINSTANCE hPrevInstance,
LPSTR lpszArgument,
int nCmdShow)
{
HWND hwnd; /* This is the handle for our window */
MSG messages; /* Here messages to the application are saved */
WNDCLASSEX wincl; /* Data structure for the windowclass */
/* The Window structure */
wincl.hInstance = hThisInstance;
wincl.lpszClassName = szClassName;
wincl.lpfnWndProc = WindowProcedure; /* This function is called by windows */
wincl.style = CS_DBLCLKS; /* Catch double-clicks */
wincl.cbSize = sizeof (WNDCLASSEX);
/* Use default icon and mouse-pointer */
wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName = NULL; /* No menu */
wincl.cbClsExtra = 0; /* No extra bytes after the window class */
wincl.cbWndExtra = 0; /* structure or the window instance */
/* Use Windows's default colour as the background of the window */
wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;
/* Register the window class, and if it fails quit the program */
if (!RegisterClassEx (&wincl))
return 0;
/* The class is registered, let's create the program*/
hwnd = CreateWindowEx (
0, /* Extended possibilites for variation */
szClassName, /* Classname */
"framebuffer project for win32", /* Title Text */
WS_OVERLAPPEDWINDOW, /* default window */
CW_USEDEFAULT, /* Windows decides the position */
CW_USEDEFAULT, /* where the window ends up on the screen */
winx, /* The programs width */
winy, /* and height in pixels */
HWND_DESKTOP, /* The window is a child-window to desktop */
NULL, /* No menu */
hThisInstance, /* Program Instance handler */
NULL /* No Window Creation data */
);
/* Make the window visible on the screen */
ShowWindow (hwnd, nCmdShow);
/* Run the message loop. It will run until GetMessage() returns 0 */
while (GetMessage (&messages, NULL, 0, 0))
{
/* Translate virtual-key messages into character messages */
TranslateMessage(&messages);
/* Send message to WindowProcedure */
DispatchMessage(&messages);
}
/* The program return-value is 0 - The value that PostQuitMessage() gave */
return messages.wParam;
}
/* This function is called by the Windows function DispatchMessage() */
LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
DWORD result;
switch (message) /* handle the messages */
{
case WM_CREATE:
{
InvalidateRect(hwnd,0,0);
}break;
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hDC = BeginPaint(hwnd, &ps);
RECT client;
GetClientRect(hwnd,&client);
if(setscanline) {
scanlinewidth = client.right;
numscanlines = client.bottom;
setscanline = 0;
}
setframebuffer();
result = StretchDIBits(hDC,
0, 0,
client.right, client.bottom,
0, 0,
scanlinewidth, numscanlines,
buffer, &m_bi, DIB_RGB_COLORS, SRCCOPY);
if(result != winy)
{
//Drawing failed
DebugBreak();
}
EndPaint(hwnd, &ps);
}break;
case WM_KEYDOWN:{ int escpressed = GetAsyncKeyState(27); if(escpressed){PostQuitMessage(0);}}break;
case WM_DESTROY: {
PostQuitMessage (0); /* send a WM_QUIT to the message queue */
}break;
default: /* for messages that we don't deal with */
return DefWindowProc (hwnd, message, wParam, lParam);
}
return 0;
}
EDIT changed int setbuffer to setbuffer in WM_create
EDIT #2 changed getdc to begin paint.
EDIT #3 changed the bpp to 24 and also changed the WM_Create to set all the bitmap properties
EDIT #4 I have found a solution thanks to your help. i didn't understand Scan Line padding before, but now i understand it perfectly. the updated code prints a solid color on the screen and you can compile it for yourself and change the color. thanks for helping me solve my problem, now i can start drawing on the screen using my own code.

Answer 1

I'm not sure all of these issues are still relevant as I copied the code before you started editing. Either way, this works and you should be able to see the differences pretty easily.
The BITMAPINFO structure was not being initialized properly.
The buffer was being created incorrectly, it was too large and not necessarily aligned properly to be used as a bitmap. The width needs to be padded to a multiple of 4 which would have been okay for a width of 500 but not for a width of 499 as an example.
I also added a check to make sure StretchDIBits was successful and it'll dump you into the debugger if it fails. You can add more appropriate error checking if you like.
I also cut some comments out just to keep things as short as possible.
#include <windows.h>
const int winx = 500;
const int winy = 500;
const int winbpp = 3;
BITMAPINFO m_bi;
char* buffer = 0;
void setbuffer()
{
m_bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
m_bi.bmiHeader.biWidth = winx;
m_bi.bmiHeader.biHeight = winy;
m_bi.bmiHeader.biPlanes = 1;
m_bi.bmiHeader.biBitCount = 24;
m_bi.bmiHeader.biCompression = BI_RGB;
m_bi.bmiHeader.biSizeImage = 0;
m_bi.bmiHeader.biXPelsPerMeter = 100;
m_bi.bmiHeader.biYPelsPerMeter = 100;
m_bi.bmiHeader.biClrUsed = 0;
m_bi.bmiHeader.biClrImportant = 0;
size_t paddedWidth = (winx * 3 + 3) & ~3;
buffer = new char[paddedWidth * winy * winbpp];
for(int y = 0; y < winy; ++y)
{
for(int x = 0; x < winx; ++x)
{
for(int z = 0; z < 3; ++z)
{
buffer[y * paddedWidth + x * winbpp + z] = z * x;
}
}
}
}
LRESULT CALLBACK WindowProcedure(HWND, UINT, WPARAM, LPARAM);
char szClassName[] = "CodeBlocksWindowsApp";
int WINAPI WinMain(HINSTANCE hThisInstance,
HINSTANCE hPrevInstance,
LPSTR lpszArgument,
int nCmdShow)
{
HWND hwnd; /* This is the handle for our window */
MSG messages; /* Here messages to the application are saved */
WNDCLASSEX wincl; /* Data structure for the windowclass */
wincl.hInstance = hThisInstance;
wincl.lpszClassName = szClassName;
wincl.lpfnWndProc = WindowProcedure; /* This function is called by windows */
wincl.style = CS_DBLCLKS; /* Catch double-clicks */
wincl.cbSize = sizeof (WNDCLASSEX);
wincl.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor(NULL, IDC_ARROW);
wincl.lpszMenuName = NULL; /* No menu */
wincl.cbClsExtra = 0; /* No extra bytes after the window class */
wincl.cbWndExtra = 0; /* structure or the window instance */
wincl.hbrBackground = (HBRUSH)COLOR_BACKGROUND;
if(!RegisterClassEx(&wincl))
return 0;
hwnd = CreateWindowEx(
0, /* Extended possibilites for variation */
szClassName, /* Classname */
" project 1 ", /* Title Text */
WS_OVERLAPPEDWINDOW, /* default window */
CW_USEDEFAULT, /* Windows decides the position */
CW_USEDEFAULT, /* where the window ends up on the screen */
winx, /* The programs width */
winy, /* and height in pixels */
HWND_DESKTOP, /* The window is a child-window to desktop */
NULL, /* No menu */
hThisInstance, /* Program Instance handler */
NULL /* No Window Creation data */
);
ShowWindow(hwnd, nCmdShow);
while(GetMessage(&messages, NULL, 0, 0))
{
TranslateMessage(&messages);
DispatchMessage(&messages);
}
return messages.wParam;
}
LRESULT CALLBACK WindowProcedure(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
HDC hDC;
RECT client;
DWORD result;
switch(message) /* handle the messages */
{
case WM_CREATE:
setbuffer();
InvalidateRect(hwnd, NULL, TRUE);
break;
case WM_PAINT:
hDC = BeginPaint(hwnd, &ps);
GetClientRect(hwnd, &client);
result = StretchDIBits(hDC,
0, 0,
client.right, client.bottom,
0, 0,
winx, winy,
buffer, &m_bi, DIB_RGB_COLORS, SRCCOPY);
if(result != winy)
{
//Drawing failed
DebugBreak();
}
EndPaint(hwnd, &ps);
break;
case WM_DESTROY:
delete buffer;
PostQuitMessage(0); /* send a WM_QUIT to the message queue */
break;
default: /* for messages that we don't deal with */
return DefWindowProc(hwnd, message, wParam, lParam);
}
return 0;
}