Write CreateDIBSection BMP Data to File - c++

Question

I have taken a screenshot programtically and I want to write out the BGRA to file. The BGRA is held in pixelBuffer.
Here is the code I am using to write to file:
BYTE *pixelBuffer;
HBITMAP hbmp;
hbmp = CreateDIBSection(hdcScreen, &bmi, DIB_RGB_COLORS, (void **)&pixelBuffer, NULL, 0);
FILE *stream;\
if (fopen_s(&stream, "C:\\Users\Vayeate\\Desktop\\blah.txt", "wb+") == 0) {
fwrite(pixelBuffer, (screenHeight * screenWidth * 4), (size_t)(sizeof(CHAR) + 1), stream); // (screenWidth * screenHeight * 4)
fclose(stream);
}
However this writes a bunch of gibberish that looks like:
òîîÿòîîÿ
And that repeat forever. I was hoping to get something like 255, 100, 100, 255.
Here is my full code:
#include <Windows.h>
#include <stdio.h>
int WINAPI WinMain(HINSTANCE hinst, HINSTANCE, LPSTR, int)
{
//Sleep(1000)
MessageBox(0, L"Hello World", L"Unipen", MB_ICONINFORMATION);
int i = 0;
DISPLAY_DEVICE device;
device.cb = sizeof(device);
while (EnumDisplayDevices(NULL, i, &device, 0) && ++i) {
if ((device.StateFlags & DISPLAY_DEVICE_ACTIVE) != DISPLAY_DEVICE_ACTIVE) {
MessageBox(0, device.DeviceName, L"CONTINUE", MB_ICONINFORMATION);
continue;
}
MessageBox(0, device.DeviceName, L"BREAK", MB_ICONINFORMATION);
break;
}
size_t screenWidth = 1920;
size_t screenHeight = 1200;
size_t colorLen = 4;
HDC hdcScreen;
hdcScreen = CreateDC(NULL, device.DeviceName, NULL, NULL);
if (hdcScreen == (HDC)NULL) {
MessageBox(0, L"UnableToCreateDC", L"ERROR", MB_ICONINFORMATION);
return 0;
}
HDC hdcMemoryDC;
hdcMemoryDC = CreateCompatibleDC(hdcScreen);
if (hdcMemoryDC == (HDC)NULL) {
DeleteDC(hdcScreen);
MessageBox(0, L"UnableToCreateCompatibleDC", L"ERROR", MB_ICONINFORMATION);
return 0;
}
BITMAPINFO bmi;
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = (LONG)screenWidth;
bmi.bmiHeader.biHeight = (-1)*(LONG)screenHeight;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
BYTE *pixelBuffer;
HBITMAP hbmp;
hbmp = CreateDIBSection(hdcScreen, &bmi, DIB_RGB_COLORS, (void **)&pixelBuffer, NULL, 0);
if (hbmp == (HBITMAP)NULL) {
DeleteDC(hdcScreen);
DeleteDC(hdcMemoryDC);
MessageBox(0, L"UnableToCreateDIBSection", L"ERROR", MB_ICONINFORMATION);
return 0;
}
//HGDIOBJ rez_selected;
HBITMAP rez_selected_bmp;
rez_selected_bmp = (HBITMAP)SelectObject(hdcMemoryDC, hbmp);
if (rez_selected_bmp == (HBITMAP)NULL) {
DeleteDC(hdcScreen);
DeleteDC(hdcMemoryDC);
DeleteObject(hbmp);
MessageBox(0, L"UnableToCreateDIBSection", L"ERROR", MB_ICONINFORMATION);
return 0;
}
BitBlt(hdcMemoryDC, 0, 0, screenWidth, screenHeight, hdcScreen, 0, 0, SRCCOPY);
//(void) SelectObject(hdcMemoryDC, rez_selected_bmp); // i dont do this step in nativeshot
FILE *stream;\
if (fopen_s(&stream, "C:\\Users\Vayeate\\Desktop\\blah.txt", "wb+") == 0) {
fwrite("asdfasdfasdf", 1, (size_t)(sizeof(CHAR) + 1), stream); // (screenWidth * screenHeight * 4)
fclose(stream);
}
DeleteDC(hdcScreen);
DeleteDC(hdcMemoryDC);
DeleteObject(hbmp);
MessageBox(0, L"DONE", L"Unipen", MB_ICONINFORMATION);
return 0;
}
How can I get space delimited BGRA data to file?

Answer 1

You're writing binary data and reading it as text. Thus, òîîÿòîîÿ is incidentally probably the correct output, as these are the characters that the binary values map to, according to the character map used by the text editor that displayed it.
If you want to have space-delimited values of the pixels in the buffer as "human-readable" ASCII written into a text file, you'll first have to use fprintf to convert these values accordingly.
Use this as an example :
if (fopen_s(&stream, "C:\\Users\Vayeate\\Desktop\\blah.txt", "w") == 0) {
for(size_t px = 0 ; px < (screenHeight * screenWidth * 4) ; ++px) {
fprintf(stream, "%hhu, ", pixelBuffer[px]);
}
fclose(stream);
}