Flip and crop a bitmap - c++

Question

I'm getting a bytearray (32 bit or 16 bit) from a source.
If the size width is odd, the last pixel in each row needs to be dropped.
If the height is odd, the last row needs to be dropped.
If the height is negative the bitmap needs to be flipped vertically.
Here is my code so far:
m_pbmiLast = new BITMAPINFO(*m_pbmi);
m_pbmiLast->bmiHeader.biWidth = abs(m_pbmiLast->bmiHeader.biWidth) - (abs(m_pbmiLast->bmiHeader.biWidth) % 2);
m_pbmiLast->bmiHeader.biHeight = abs(m_pbmiLast->bmiHeader.biHeight) - (abs(m_pbmiLast->bmiHeader.biHeight) % 2);
int biWidth = m_pbmiLast->bmiHeader.biWidth;
int biHeight = m_pbmiLast->bmiHeader.biHeight;
int iAdjustedStride = ((((biWidth * m_pbmiLast->bmiHeader.biBitCount) + 31) & ~31) >> 3);
int iRealStride = ((((m_pbmi->bmiHeader.biWidth * m_pbmi->bmiHeader.biBitCount) + 31) & ~31) >> 3);
if (m_pbmi->bmiHeader.biHeight < 0) {
/* Copy the actual data */
int iLineOffsetSource = 0;
int iLineOffsetDest = (biHeight - 1) * iRealStride;
for (int i = 0; i < biHeight; ++i) {
memcpy(&pData[iLineOffsetDest], &m_inputBuffer[iLineOffsetSource], iAdjustedStride);
iLineOffsetSource += iRealStride;
iLineOffsetDest -= iRealStride;
}
} else {
int iLineOffset = 0;
for (int i = 0; i < biHeight; ++i) {
memcpy(&pData[iLineOffset], &m_inputBuffer[iLineOffset], iAdjustedStride);
iLineOffset += iRealStride;
}
}
It doesn't flip the bitmap, and when the bitmap is an odd width, it slants the bitmap.

Answer 1

Can be done like so.. I include the reading and writing just to make it an SSCCE. It has little to no error.
As for my comment about new BITMAPINFO. I was saying that you don't have to allocate such a small structure on the HEAP. Ditch the new part. The only allocation you need for a bitmap is the pixels. The header and other info does not need an allocation at all.
See the Flip function below.
#include <iostream>
#include <fstream>
#include <cstring>
#include <windows.h>
typedef struct
{
BITMAPFILEHEADER Header;
BITMAPINFO Info;
unsigned char* Pixels;
} BITMAPDATA;
void LoadBmp(const char* path, BITMAPDATA* Data)
{
std::ifstream hFile(path, std::ios::in | std::ios::binary);
if(hFile.is_open())
{
hFile.read((char*)&Data->Header, sizeof(Data->Header));
hFile.read((char*)&Data->Info, sizeof(Data->Info));
hFile.seekg(Data->Header.bfOffBits, std::ios::beg);
Data->Pixels = new unsigned char[Data->Info.bmiHeader.biSizeImage];
hFile.read((char*)Data->Pixels, Data->Info.bmiHeader.biSizeImage);
hFile.close();
}
}
void SaveBmp(const char* path, BITMAPDATA* Data)
{
std::ofstream hFile(path, std::ios::out | std::ios::binary);
if (hFile.is_open())
{
hFile.write((char*)&Data->Header, sizeof(Data->Header));
hFile.write((char*)&Data->Info, sizeof(Data->Info));
hFile.seekp(Data->Header.bfOffBits, std::ios::beg);
hFile.write((char*)Data->Pixels, Data->Info.bmiHeader.biSizeImage);
hFile.close();
}
}
void Flip(BITMAPDATA* Data)
{
unsigned short bpp = Data->Info.bmiHeader.biBitCount;
unsigned int width = std::abs(Data->Info.bmiHeader.biWidth);
unsigned int height = std::abs(Data->Info.bmiHeader.biHeight);
unsigned char* out = new unsigned char[Data->Info.bmiHeader.biSizeImage];
unsigned long chunk = (bpp > 24 ? width * 4 : width * 3 + width % 4);
unsigned char* dst = out;
unsigned char* src = Data->Pixels + chunk * (height - 1);
while(src != Data->Pixels)
{
std::memcpy(dst, src, chunk);
dst += chunk;
src -= chunk;
}
std::memcpy(dst, src, chunk); //for 24-bit.
std::swap(Data->Pixels, out);
delete[] out;
}
int main()
{
BITMAPDATA Data;
LoadBmp("C:/Users/Brandon/Desktop/Bar.bmp", &Data);
Flip(&Data);
SaveBmp("C:/Users/Brandon/Desktop/Foo.bmp", &Data);
delete[] Data.Pixels;
return 0;
}