scbc_repos/CTSManager/CTSManager/ImageHelper.cpp

#include "pch.h"
#include "ImageHelper.h"
#include <shlwapi.h>

bool CImageHelper::SaveBitmapToFile(HBITMAP hBitmap, const std::string& filename)
{
	//1. 创建位图文件
	const auto file = CreateFileA(filename.c_str(), GENERIC_WRITE,
		0, nullptr, CREATE_ALWAYS,
		FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
		nullptr);
	if (file == INVALID_HANDLE_VALUE)
	{
		return false;
	}

	//2. 计算位图文件每个像素所占字节数
	const auto bitCount = GetBitmapBitCount();

	//3. 获取位图结构
	BITMAP bitmap;
	::GetObject(hBitmap, sizeof(bitmap), reinterpret_cast<LPSTR>(&bitmap));

	//位图中像素字节大小(32字节对齐)
	const DWORD bmBitsSize = ((bitmap.bmWidth * bitCount + 31) / 32) * 4 * bitmap.bmHeight;

	//调色板大小
	const DWORD paletteSize = 0;

	//4. 构造位图信息头
	BITMAPINFOHEADER  bmpInfoHeader; //位图信息头结构
	bmpInfoHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmpInfoHeader.biWidth = bitmap.bmWidth;
	bmpInfoHeader.biHeight = bitmap.bmHeight;
	bmpInfoHeader.biPlanes = 1;
	bmpInfoHeader.biBitCount = bitCount;
	bmpInfoHeader.biCompression = BI_RGB;
	bmpInfoHeader.biSizeImage = 0;
	bmpInfoHeader.biXPelsPerMeter = 0;
	bmpInfoHeader.biYPelsPerMeter = 0;
	bmpInfoHeader.biClrImportant = 0;
	bmpInfoHeader.biClrUsed = 0;

	//5. 构造位图文件头
	BITMAPFILEHEADER bmpFileHeader;
	bmpFileHeader.bfType = 0x4D42; //"BM"
	//位图文件大小
	const DWORD dibSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + paletteSize + bmBitsSize;
	bmpFileHeader.bfSize = dibSize;
	bmpFileHeader.bfReserved1 = 0;
	bmpFileHeader.bfReserved2 = 0;
	bmpFileHeader.bfOffBits = static_cast<DWORD>(sizeof(BITMAPFILEHEADER))
		+ static_cast<DWORD>(sizeof(BITMAPINFOHEADER)) + paletteSize;

	//6. 为位图内容分配内存 
	const auto dib = GlobalAlloc(GHND, bmBitsSize + paletteSize + sizeof(BITMAPINFOHEADER)); //内存句柄
	const auto lpBmpInfoHeader = static_cast<LPBITMAPINFOHEADER>(GlobalLock(dib)); //指向位图信息头结构
	*lpBmpInfoHeader = bmpInfoHeader;

	//7. 处理调色板
	ProcessPalette(hBitmap, bitmap, paletteSize, lpBmpInfoHeader);

	//8. 写入文件
	DWORD written = 0; //写入文件字节数   
	WriteFile(file, reinterpret_cast<LPSTR>(&bmpFileHeader), sizeof(BITMAPFILEHEADER),
		&written, nullptr); //写入位图文件头
	WriteFile(file, reinterpret_cast<LPSTR>(lpBmpInfoHeader), dibSize,
		&written, nullptr); //写入位图文件其余内容

	//9. 清理资源
	GlobalUnlock(dib);
	GlobalFree(dib);
	CloseHandle(file);

	return true;
}

//计算位图文件每个像素所占字节数
WORD CImageHelper::GetBitmapBitCount()
{
	const auto dc = ::CreateDCA("DISPLAY", nullptr, nullptr, nullptr);
	//当前分辨率下每像素所占字节数
	const auto bits = ::GetDeviceCaps(dc, BITSPIXEL) * GetDeviceCaps(dc, PLANES);
	::DeleteDC(dc);

	//位图中每像素所占字节数
	WORD bitCount;
	if (bits <= 1)
		bitCount = 1;
	else if (bits <= 4)
		bitCount = 4;
	else if (bits <= 8)
		bitCount = 8;
	else
		bitCount = 24;

	return bitCount;
}

//处理调色板
void CImageHelper::ProcessPalette(HBITMAP hBitmap, const BITMAP& bitmap,
	DWORD paletteSize, LPBITMAPINFOHEADER lpBmpInfoHeader)
{
	HANDLE oldPalette = nullptr;
	HDC dc = nullptr;
	const auto palette = GetStockObject(DEFAULT_PALETTE);
	if (palette != nullptr)
	{
		dc = ::GetDC(nullptr);
		oldPalette = ::SelectPalette(dc, static_cast<HPALETTE>(palette), FALSE);
		::RealizePalette(dc); //实现设备调色板
	}

	//获取该调色板下新的像素值
	GetDIBits(dc, hBitmap, 0, static_cast<UINT>(bitmap.bmHeight),
		reinterpret_cast<LPSTR>(lpBmpInfoHeader) + sizeof(BITMAPINFOHEADER) + paletteSize,
		reinterpret_cast<BITMAPINFO*>(lpBmpInfoHeader), DIB_RGB_COLORS);

	//恢复调色板
	if (oldPalette != nullptr)
	{
		::SelectPalette(dc, static_cast<HPALETTE>(oldPalette), TRUE);
		::RealizePalette(dc);
		::ReleaseDC(nullptr, dc);
	}
}