Creating an HBITMAP from pixel buffer then rendering - c

Question

Ok, so I literally just started using the WinAPI for drawing bitmap images. So if my code is absolute trash, I apologize. Anyways, how the heck am I supposed to do this? Essentially, I want to create an HBITMAP object from a simple unsigned char pixel buffer using CreateBitmap() like this...
HBITMAP hbm = CreateBitmap(width, height, 1, 24, buffer);
(obviously this is 3-bytes per pixel)
That appears to work fine until I try rendering it. For now, I just wanted to keep it simple and draw a 100 by 100 black pixel square on the screen but nothing shows up. I would appreciate it if anyone could point out the mistakes in my atrocious code.
This is my setup (I am aware a lot of things could be improved I just wanted to go as minimalistic as possible for now and actually have something appear on the screen):
HBITMAP hbm = NULL;
void window_init(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
static unsigned char buffer[30000] = {0};
hbm = CreateBitmap(100, 100, 1, 24, buffer);
}
void window_draw(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
HDC hdc = BeginPaint(hwnd, &ps);
HDC hdcMem = CreateCompatibleDC(hdc);
HBITMAP hbmOld = SelectObject(hdcMem, hbm);
BitBlt(hdc, 100, 100, 100, 100, hdcMem, 0, 0, SRCCOPY);
SelectObject(hdcMem, hbmOld);
DeleteDC(hdcMem);
EndPaint(hwnd, &ps);
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
switch (msg) {
case WM_CREATE: window_init(hwnd, msg, wParam, lParam); break;
case WM_PAINT: window_draw(hwnd, msg, wParam, lParam); break;
case WM_CLOSE: DestroyWindow(hwnd); break;
case WM_DESTROY: PostQuitMessage(0); break;
default: return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
Here's my entire code in case you want to copy it...
#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
typedef struct {
const char *wc_name;
const char *title;
unsigned int width;
unsigned int height;
} Window;
static HBITMAP hbmp = NULL;
static PAINTSTRUCT ps;
void window_create(Window *window, const char *wc_name, const char *title, unsigned int width, unsigned int height) {
window->wc_name = wc_name;
window->title = title;
window->width = width;
window->height = height;
}
void window_init(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
static unsigned char buffer[30000] = {0};
hbmp = CreateBitmap(100, 100, 1, 24, buffer);
}
void window_draw(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
HDC hdc = BeginPaint(hwnd, &ps);
HDC hdcMem = CreateCompatibleDC(hdc);
HBITMAP hbmOld = SelectObject(hdcMem, hbmp);
BitBlt(hdc, 100, 100, 100, 100, hdcMem, 0, 0, SRCCOPY);
SelectObject(hdcMem, hbmOld);
DeleteDC(hdcMem);;
EndPaint(hwnd, &ps);
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
switch (msg) {
case WM_CREATE: window_init(hwnd, msg, wParam, lParam); break;
case WM_PAINT: window_draw(hwnd, msg, wParam, lParam); break;
case WM_CLOSE: DestroyWindow(hwnd); break;
case WM_DESTROY: PostQuitMessage(0); break;
default: return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) {
Window window;
window_create(&window, "Parent Window", "My Window", 1000, 1000 / 16 * 9);
WNDCLASSEX wc = {0};
MSG msg = {0};
HWND hwnd = NULL;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = WndProc;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);
wc.lpszClassName = window.wc_name;
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
if (!RegisterClassEx(&wc)) {
MessageBox(NULL, "Failed to register application window!", "WC Registration Error!", MB_ICONEXCLAMATION | MB_OK);
return -1;
}
hwnd = CreateWindowEx(
0, window.wc_name, window.title,
WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT,
window.width, window.height, NULL, NULL, hInstance, NULL
);
if (!hwnd) {
MessageBox(NULL, "Failed to launch application window!", "HWND Creation Error!", MB_ICONEXCLAMATION | MB_OK);
return -1;
}
ShowWindow(hwnd, SW_MAXIMIZE);
UpdateWindow(hwnd);
while (GetMessage(&msg, NULL, 0, 0) > 0) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}

Answer 1

CreateBitmap produces a handle to a device dependent bitmap unlike CreateDIBSection which is guaranteed to create a device-independent bitmap with the device context if it succeeds, and allows you access to the actual bits in the bitmap, unlike CreateCompatibleBitmap.
How to use CreateDIBSection:
HDC hdc = GetDC(hwnd);
BITMAPINFO bi = { 0 };
static BYTE *bits = NULL;
static unsigned char buffer[30000] = { 0 };
bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bi.bmiHeader.biWidth = 100;
bi.bmiHeader.biHeight = -100;
bi.bmiHeader.biPlanes = 1;
bi.bmiHeader.biBitCount = 24;
bi.bmiHeader.biCompression = BI_RGB;
hbmp = CreateDIBSection(hdc, &bi, DIB_RGB_COLORS, (void**)&bits, NULL, 0);
CopyMemory(bits, buffer, 30000);
ReleaseDC(hwnd, hdc);