gpt4 book ai didi

c++ - 将 Windows BITMAP 转换为 PIX(无符号字符缓冲区)

转载 作者:行者123 更新时间:2023-11-28 05:40:33 25 4
gpt4 key购买 nike

我正在截取一个窗口的屏幕截图,以便使用 Leptonica 对其进行处理,然后使用 Tesseract 进行一些 OCR

问题是,在性能方面,我想避免将 BMP 写入和读取到光盘,而只是在内存中工作。这就是我制作屏幕截图的方式:

int width, height = 0;

HDC hdcWindow;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
BITMAP bmpScreen;

// Retrieve the handle to a display device context for the client
// area of the window.
//hdcScreen = GetDC(NULL);
//hdcWindow = GetDC(hWnd);

hdcWindow = GetDC(hWnd);

// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcWindow);

if (!hdcMemDC)
{
MessageBox(hWnd, L"CreateCompatibleDC has failed", L"Failed", MB_OK);
goto done;
}

// Get the client area for size calculation
RECT rcClient;
GetClientRect(hWnd, &rcClient);


// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcWindow, rcClient.right - rcClient.left, rcClient.bottom - rcClient.top);

if (!hbmScreen)
{
MessageBox(hWnd, L"CreateCompatibleBitmap Failed", L"Failed", MB_OK);
goto done;
}

// Select the compatible bitmap into the compatible memory DC.
SelectObject(hdcMemDC, hbmScreen);

// Bit block transfer into our compatible memory DC.
if (!BitBlt(hdcMemDC,
0, 0,
rcClient.right - rcClient.left, rcClient.bottom - rcClient.top,
hdcWindow,
0, 0,
SRCCOPY))
{
MessageBox(hWnd, L"BitBlt has failed", L"Failed", MB_OK);
goto done;
}

// Get the BITMAP from the HBITMAP
GetObject(hbmScreen, sizeof(BITMAP), &bmpScreen);

BITMAPFILEHEADER bmfHeader;
BITMAPINFOHEADER bi;

bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bmpScreen.bmWidth;
bi.biHeight = bmpScreen.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = 32;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

DWORD dwBmpSize = ((bmpScreen.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmpScreen.bmHeight;

// Starting with 32-bit Windows, GlobalAlloc and LocalAlloc are implemented as wrapper functions that
// call HeapAlloc using a handle to the process's default heap. Therefore, GlobalAlloc and LocalAlloc
// have greater overhead than HeapAlloc.
HANDLE hDIB = GlobalAlloc(GHND, dwBmpSize);
char *lpbitmap = (char *)GlobalLock(hDIB);

// Gets the "bits" from the bitmap and copies them into a buffer
// which is pointed to by lpbitmap.
GetDIBits(hdcWindow, hbmScreen, 0,
(UINT)bmpScreen.bmHeight,
lpbitmap,
(BITMAPINFO *)&bi, DIB_RGB_COLORS);

// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(L"pics/UI.bmp",
GENERIC_WRITE,
0,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL, NULL);

// Add the size of the headers to the size of the bitmap to get the total file size
DWORD dwSizeofDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

//Offset to where the actual bitmap bits start.
bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);

//Size of the file
bmfHeader.bfSize = dwSizeofDIB;

//bfType must always be BM for Bitmaps
bmfHeader.bfType = 0x4D42; //BM

DWORD dwBytesWritten = 0;
WriteFile(hFile, (LPSTR)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)lpbitmap, dwBmpSize, &dwBytesWritten, NULL);

//Unlock and Free the DIB from the heap
GlobalUnlock(hDIB);
GlobalFree(hDIB);

//Close the handle for the file that was created
CloseHandle(hFile);

width = rcClient.right - rcClient.left;
height = rcClient.bottom - rcClient.top;

//Clean up
done:
DeleteObject(hbmScreen);
DeleteObject(hdcMemDC);
ReleaseDC(hWnd, hdcWindow);

我是这样读的:

PIX* pixUI = pixRead("pics/UI.bmp");

所以,我看到库有一个 PIX * pixReadMemBmp ( const l_uint8 *cdata, size_t size ) method它需要一个 l_uint8,它是一个 unsigned char 缓冲区

问题是,我不明白如何从我的 HBITMAPBITMAP 对象中获取这样的缓冲区。

最佳答案

首先将位图复制到缓冲区中,然后将此缓冲区交给pixReadMemBmp()。必须进行复制,因为我认为 pixReadMemBmp() 函数需要位图数据前面的两个位图 header ,就像在文件中一样。伪代码:

std::vector<unsigned char> buffer(sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + dwBmpSize);
std::copy(reinterpret_cast<unsigned char*>(&bmfHeader), reinterpret_cast<unsigned char*>(&bmfHeader) + sizeof(BITMAPFILEHEADER), buffer.begin());
std::copy(reinterpret_cast<unsigned char*>(&bi), reinterpret_cast<unsigned char*>(&bi) + sizeof(BITMAPINFOHEADER), buffer.begin() + sizeof(BITMAPFILEHEADER));
std::copy(lpbitmap, lpbitmap + dwBmpSize, buffer.begin() + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER));
pixReadMemBmp(&buffer[0], buffer.size());

关于c++ - 将 Windows BITMAP 转换为 PIX(无符号字符缓冲区),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/37205992/

25 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com