How to increase bitmap pixel size? [closed] - c++

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I'm struggling to find the way to increase pixel sizes in a win32 bitmap. Is there any way to do it?
I made a small win32 program below. When you run it, you should get a window with a very tiny red dot in the center. You can use up, down, left, and right arrow keys to control the dot.
/* compile: gcc test.c -o test -lgdi32 -Wl,-subsystem,windows */
// TODO fast way to update? resize pixel size? best coding practices?
#include <windows.h>
#define WND_WIDTH 500
#define WND_HEIGHT 500
#define ID_TIMER 1
void DrawBitmap(HDC hdc, RECT *rect, BITMAPINFO info, void *bmpMem)
{
int width = rect->right - rect->left;
int height = rect->bottom - rect->top;
StretchDIBits(hdc,
0,
0,
info.bmiHeader.biWidth,
info.bmiHeader.biHeight,
0,
0,
width,
height,
bmpMem,
&info,
DIB_RGB_COLORS,
SRCCOPY);
}
void UpdateBitmap(BITMAPINFO info, void *bmpMem, POINT pix)
{
int width = info.bmiHeader.biWidth;
int height = info.bmiHeader.biHeight;
BYTE *pixel = (BYTE *) bmpMem;
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
if (x == pix.x && y == pix.y)
{
*pixel++ = 0; /* blue */
*pixel++ = 0; /* green */
*pixel++ = 255; /* red */
*pixel++ = 255; /* alpha */
}
else
{
*pixel++ = 0; /* blue */
*pixel++ = 0; /* green */
*pixel++ = 0; /* red */
*pixel++ = 255; /* alpha */
}
}
}
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
static BITMAPINFO info;
static void *bmpMem;
static POINT pixel;
switch (msg)
{
case WM_CREATE:
{
RECT rcClient;
GetClientRect(hWnd, &rcClient);
int width = rcClient.right - rcClient.left;
int height = rcClient.bottom - rcClient.top;
info.bmiHeader.biSize = sizeof(info.bmiHeader);
info.bmiHeader.biWidth = width;
info.bmiHeader.biHeight = height;
info.bmiHeader.biPlanes = 1;
info.bmiHeader.biBitCount = 32;
info.bmiHeader.biCompression = BI_RGB;
info.bmiHeader.biSizeImage = 0;
info.bmiHeader.biXPelsPerMeter = 0;
info.bmiHeader.biYPelsPerMeter = 0;
info.bmiHeader.biClrUsed = 0;
info.bmiHeader.biClrImportant = 0;
bmpMem = VirtualAlloc(0, width * height * 4, MEM_COMMIT, PAGE_READWRITE);
pixel.x = width / 2;
pixel.y = height / 2;
if(!SetTimer(hWnd, ID_TIMER, 50, NULL))
{
MessageBox(hWnd, "Could not SetTimer()!", "Error", MB_OK | MB_ICONEXCLAMATION);
PostQuitMessage(1);
}
break;
}/*
case WM_PAINT:
{
RECT rcClient;
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
GetClientRect(hWnd, &rcClient);
DrawBitmap(hdc, &rcClient, info, bmpMem);
EndPaint(hWnd, &ps);
break;
}*/
case WM_TIMER:
{
RECT rcClient;
HDC hdc = GetDC(hWnd);
GetClientRect(hWnd, &rcClient);
UpdateBitmap(info, bmpMem, pixel);
DrawBitmap(hdc, &rcClient, info, bmpMem);
ReleaseDC(hWnd, hdc);
break;
}
case WM_KEYDOWN:
{
switch (wParam)
{
case VK_LEFT: pixel.x -= 1; break;
case VK_RIGHT: pixel.x += 1; break;
case VK_UP: pixel.y += 1; break;
case VK_DOWN: pixel.y -= 1; break;
}
break;
}
case WM_CLOSE:
DestroyWindow(hWnd);
break;
case WM_DESTROY:
KillTimer(hWnd, ID_TIMER);
VirtualFree(bmpMem, 0, MEM_RELEASE);
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, msg, wParam, lParam);
}
return 0;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
const TCHAR szClassName[] = TEXT("MyClass");
WNDCLASS wc;
HWND hWnd;
MSG msg;
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wc.lpszMenuName = NULL;
wc.lpszClassName = szClassName;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
if (!RegisterClass(&wc))
{
MessageBox(NULL, TEXT("Window Registration Failed!"), TEXT("Error!"),
MB_ICONEXCLAMATION | MB_OK);
return 1;
}
hWnd = CreateWindow(szClassName,
TEXT("Title"),
WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX, /* this window style prevents window resizing */
CW_USEDEFAULT,
CW_USEDEFAULT,
WND_WIDTH,
WND_HEIGHT,
NULL,
NULL,
hInstance,
NULL);
if (hWnd == NULL)
{
MessageBox(NULL, TEXT("Window Creation Failed!"), TEXT("Error!"),
MB_ICONEXCLAMATION | MB_OK);
return 1;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
while (GetMessage(&msg, NULL, 0, 0) > 0)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return (int) msg.wParam;
}
I want to increase the size of the tiny red dot and all other pixels in the bitmap. I tried to decrease the width and height like this
switch (msg)
{
case WM_CREATE:
{
//RECT rcClient;
//GetClientRect(hWnd, &rcClient);
int width = 30;
int height = 30;
I expected to see a big red dot at the center but I got the white screen instead. How can I edit the code to display bigger pixels?

Answer 1

You are creating a single red pixel in your UpdateBitmap:
if (x == pix.x && y == pix.y)
{
*pixel++ = 0; /* blue */
*pixel++ = 0; /* green */
*pixel++ = 255; /* red */
*pixel++ = 255; /* alpha */
}
If you want a bigger "dot" - define a radius somewhere:
int r = 17;
and change your condition to
if ((x - pix.x)* (x - pix.x) + (y - pix.y)* (y - pix.y) <= r*r)
To scale the entire bitmap, modify DrawBitmap:
void DrawBitmap(HDC hdc, RECT* rect, BITMAPINFO info, void* bmpMem)
{
int width = rect->right - rect->left;
int height = rect->bottom - rect->top;
int scale = 7;
StretchDIBits(hdc,
-(info.bmiHeader.biWidth * scale - width) / 2,
-(info.bmiHeader.biHeight * scale - height) / 2,
info.bmiHeader.biWidth * scale,
info.bmiHeader.biHeight * scale,
0,
0,
width,
height,
bmpMem,
&info,
DIB_RGB_COLORS,
SRCCOPY);
}
StretchDIBits will stretch (or shrink) the area of the source (specified by 0, 0, width, height) into some are of the destination.
In this example, I magnified the size of the destination by the factor of scale - so the image will stretch. The negative offset is to "center" the image over destination; you can use 0,0 to keep the top-left anchor.