How do I write raw pixel data and save as a bitmap - c++

Question

My problem is this: I wanna try to make a white color 24bit bitmap, but everytime I write to the bmp file, it gives me white black/white stripes. i dont understand why? Maybe i skip some bytes?
If you want more information on the code just ask.
setup settings:
void setup_settings( ) {
// information om billedet
pic.infoHeader.biSize = sizeof(BMP_InfoHeader);
pic.infoHeader.biBitCount = 24;
pic.infoHeader.biWidth = WIDTH; // Hoejte i pixels
pic.infoHeader.biHeight = HEIGH; // bredte i pixels
pic.infoHeader.biPlanes = 1;
pic.infoHeader.biCompression = 0;
pic.infoHeader.biSizeImage = WIDTH * HEIGH * (pic.infoHeader.biBitCount/8);
pic.infoHeader.biXPelsPerMeter = 0;
pic.infoHeader.biYPelsPerMeter = 0;
pic.infoHeader.biClrUsed = 0;
pic.infoHeader.biClrInportant = 0;
pic.fileHeader.bfType[0] = 'B';
pic.fileHeader.bfType[1] = 'M';
pic.fileHeader.bfReservered1 = pic.fileHeader.bfReservered2 = 0;
pic.fileHeader.bfOffBits = sizeof(BMP_FileHeader) + pic.infoHeader.biSize;
}
this funktion definition for my SaveBitmapFile is:
int SaveBitmapFile(const std::string filename, bit24* image){
// gem filen
std::ofstream writer(FileName.c_str(), std::ofstream::binary);
if(!writer.is_open()){
printf("Error: While Writing\n");
return -1;
}
writer.write(reinterpret_cast<char *>(&pic.fileHeader), sizeof(BMP_FileHeader) );
writer.write(reinterpret_cast<char *>(&pic.infoHeader), sizeof(BMP_InfoHeader) );
writer.write(reinterpret_cast<char*>(&image[0]), pic.infoHeader.biSizeImage);
writer.close();
return 0;
}
My structures:
#pragma pack(1)
typedef struct{
uint32_t value : 24;
}bit24;
#pragma pack(0)
// Billedet
#pragma pack(1)
typedef struct{
unsigned int Width;
unsigned int Heigh;
bit24* RGB;
}Image;
#pragma pack(0)
typedef struct {
BMP_FileHeader fileHeader;
BMP_InfoHeader infoHeader;
Image data;
}BMP_Data;
My source main source code:
// the pic is a type of BMP_Data. sorry if i this is really messy.
int main( int argc, char *argv[] ){
setup_settings();
pic.data.Heigh = pic.infoHeader.biHeight;
pic.data.Width = pic.infoHeader.biWidth;
int bytesPerRGB = (pic.infoHeader.biBitCount/8);
//padded bytes?
int paddedBytes = ( pic.data.Width * bytesPerRGB) % 4;
printf("PaddedBytes: %d\n", paddedBytes);
pic.data.RGB = new bit24[ pic.data.Heigh * pic.data.Width * bytesPerRGB];
uint8_t r,g,b;
r = 0xFF;
g = 0xFF;
b = 0xFF;
/*
for( unsigned int y = 0; y < pic.data.Heigh; y++)
for( unsigned int x = 0; x < pic.data.Width; x++)
{
pic.data.RGB[x + (y*pic.data.Width )].value = ( (b << 0) | (g << 8) | (r << 16) );
}
*/
for( unsigned int i = 0; i < pic.data.Heigh * pic.data.Width * bytesPerRGB; i+=3){
pic.data.RGB[i ].value = ( (b << 0) | (g << 8) | (r << 16) );
}
SaveBitmapFile(FileName, pic.data.RGB);
delete [] pic.data.RGB;
return 0;
}

Answer 1

You MUST fill all BitmapInfoHeader fields.
- Assuming you want 24bits bitmap:
BITMAPINFOHEADER bi =
{
sizeof(BITMAPINFOHEADER), // DWORD, = 40
WIDTH, // DWORD, image width in pix
HEIGHT, // DWORD, image width in pix
1, // WORD, planes MUST be 1
24,// WORD, num of bits per pixel
BI_RGB, // DWORD, (no compression = BI_RGB = 0)
0, // DWORD, sizeof image data, can be 0 if BI_RGB = 0
0, // DWORD, x-resolution
0, // DWORD, y-resolution
0, // DWORD, colors used (palette images only)
0, // DWORD, importand colors (palette images only)
};
Also make sure every row (horizontal line) of pixels is padded to multiple of 4 bytes !!!
(So begin with images of N x 4 width - they have no padding issues)

Answer 2

Okay, I have found the problem.
After I changed the bit24 to:
typedef struct{
uint8_t blue;
uint8_t green;
uint8_t red;
}RGB_Data;
from:
#pragma pack(1)
typedef struct{
uint32_t value : 24;
}bit24;
#pragma pack(0)
and a little change in the main:
for( unsigned int i = 0; i < pic.data.Heigh * pic.data.Width * bytesPerRGB; i++){
pic.data.RGB[i].blue = b;
pic.data.RGB[i].green = g;
pic.data.RGB[i].red = r;
}
it worked like a charm. thanx you for your help :)