How to convert an Array of pixels to HBITMAP

c++, createdibsection, dib, winforms

Solution

I found how to do it. We need to use `CreateDIBSection()` instead of `CreateDIBitmap()` So here is the working code

HBITMAP hBitmap = NULL;
    unsigned char pixels[160*120*3]; 
    for (int i=0; i<160*120*3; i++){
        pixels[i] = (i%4==1)*255;        // An BGR (not RGB) 160x120 image.
    }
BITMAPINFOHEADER bmih;
bmih.biSize     = sizeof(BITMAPINFOHEADER);
bmih.biWidth    = 160;
bmih.biHeight   = -120;
bmih.biPlanes   = 1;
bmih.biBitCount = 24;
bmih.biCompression  = BI_RGB ;
bmih.biSizeImage    = 0;
bmih.biXPelsPerMeter    =   10;
bmih.biYPelsPerMeter    =   10;
bmih.biClrUsed    =0;
bmih.biClrImportant =0;

BITMAPINFO dbmi;
ZeroMemory(&dbmi, sizeof(dbmi));  
dbmi.bmiHeader = bmih;
dbmi.bmiColors->rgbBlue = 0;
dbmi.bmiColors->rgbGreen = 0;
dbmi.bmiColors->rgbRed = 0;
dbmi.bmiColors->rgbReserved = 0;
void* bits = (void*)&(pixels[0]); 

// Create DIB
hBitmap = CreateDIBSection(localDC, &dbmi, DIB_RGB_COLORS, &bits, NULL, 0);
if (hBitmap == NULL) {
    ::MessageBox(NULL, __T("Could not load the desired image image"), __T("Error"), MB_OK);
    return;
}
// copy pixels into DIB.
memcpy(bits,pixels,sizeof(pixels));

For grey level images, copy the pixels to DIB in a loop instead of with memcpy()

#define INTENSITY unsigned char

INTENSITY* dest = (INTENSITY*)bits;
const INTENSITY* src  = .. Put your char array of pixels;
for (int j=0; j<imageWidth; j++){
    for (int i=0; i<imageHeight; i++, src++){
        *dest++ = *src;
        *dest++ = *src;
        *dest++ = *src;
    }
    // Padd the line to round WORD.
    if (imageWidth%2)
        *dest++ = 0;
}  

Problem

I have an array of pixels which I need to convert to HBITMAP in order to display it in a window. I tried to use CreateDIBitmap() but I don't have the BMP headers. I tried to construct them manually according to MSDN documentation but this didn't work. Here how my code looks ``` HBITMAP hBitmap char pixels[160*120]; // White grayscale image of size 160x120 memset(pixels,255,sizeof(pixels)); BITMAPINFOHEADER bmih; bmih.biSize = sizeof(BITMAPINFOHEADER); bmih.biWidth = 160; bmih.biHeight = -120; bmih.biPlanes = 1; bmih.biBitCount = 8; bmih.biCompression = BI_RGB ; bmih.biSizeImage = 0; bmih.biXPelsPerMeter = 10; bmih.biYPelsPerMeter = 10; bmih.biClrUsed =0; bmih.biClrImportant =0; BITMAPINFO dbmi; dbmi.bmiHeader = bmih; dbmi.bmiColors->rgbBlue = 0; dbmi.bmiColors->rgbGreen = 0; dbmi.bmiColors->rgbRed = 0; dbmi.bmiColors->rgbReserved = 0; void* bits = (void*)&(pixels[0]); hBitmap = CreateDIBitmap(localDC, &bmih, CBM_INIT, qB.bmBits, &dbmi, DIB_RGB_COLORS); ``` Now I get a non NULL hBitmap which is good but it shows always black image as if it doesn't point to the array of pixels. I checked it using the code ``` BITMAP qB; GetObject(reinterpret_cast<HGDIOBJ>(hBitmap),sizeof(BITMAP),reinterpret_cast<LPVOID>(&qB)); ``` And indeed qB.bmBits is NULL. What is the problem and how to fix it?

Original source