如何从屏幕上的坐标读取tesseract-ocr？

Question

我一直试图寻找一个如何创建一个类/函数的例子，该类/函数试图从指定坐标的屏幕读取文本。

一些简单的东西，可以使用bitblt捕获屏幕的指定部分并在其上运行tesseract。 所有内容都在内存中完成，无需将图像文件创建到磁盘。

Tesseract似乎有非常糟糕的API并且需要所有东西的TIF图像，据我所知它甚至不能接受位图内存图像而不需要对其代码进行大量深入研究。

任何帮助将不胜感激，一个实际的例子将是理想的。

Answer 1

http://i.imgur.com/HaJ2zOI.png

阅读/查看以下内容，了解如何将Tesseract-OCR与内存中的图像一起使用。

#include <iostream>
#include <vector>
#include <stdexcept>
#include <fstream>
#include <memory>
#include <cstring>
#include <tesseract/baseapi.h>
#include <leptonica/allheaders.h>

#if defined _WIN32 || defined _WIN64
#include <windows.h>
#endif

class Image
{
    private:
        std::vector<std::uint8_t> Pixels;
        std::uint32_t width, height;
        std::uint16_t BitsPerPixel;

        void Flip(void* In, void* Out, int width, int height, unsigned int Bpp);

    public:
        #if defined _WIN32 || defined _WIN64
        explicit Image(HDC DC, int X, int Y, int Width, int Height);
        #endif

        inline std::uint16_t GetBitsPerPixel() {return this->BitsPerPixel;}
        inline std::uint16_t GetBytesPerPixel() {return this->BitsPerPixel / 8;}
        inline std::uint16_t GetBytesPerScanLine() {return (this->BitsPerPixel / 8) * this->width;}
        inline int GetWidth() const {return this->width;}
        inline int GetHeight() const {return this->height;}
        inline const std::uint8_t* GetPixels() {return this->Pixels.data();}
};

void Image::Flip(void* In, void* Out, int width, int height, unsigned int Bpp)
{
   unsigned long Chunk = (Bpp > 24 ? width * 4 : width * 3 + width % 4);
   unsigned char* Destination = static_cast<unsigned char*>(Out);
   unsigned char* Source = static_cast<unsigned char*>(In) + Chunk * (height - 1);

   while(Source != In)
   {
      std::memcpy(Destination, Source, Chunk);
      Destination += Chunk;
      Source -= Chunk;
   }
}

#if defined _WIN32 || defined _WIN64
Image::Image(HDC DC, int X, int Y, int Width, int Height) : Pixels(), width(Width), height(Height), BitsPerPixel(32)
{
    BITMAP Bmp = {0};
    HBITMAP hBmp = reinterpret_cast<HBITMAP>(GetCurrentObject(DC, OBJ_BITMAP));

    if (GetObject(hBmp, sizeof(BITMAP), &Bmp) == 0)
        throw std::runtime_error("BITMAP DC NOT FOUND.");

    RECT area = {X, Y, X + Width, Y + Height};
    HWND Window = WindowFromDC(DC);
    GetClientRect(Window, &area);

    HDC MemDC = GetDC(nullptr);
    HDC SDC = CreateCompatibleDC(MemDC);
    HBITMAP hSBmp = CreateCompatibleBitmap(MemDC, width, height);
    DeleteObject(SelectObject(SDC, hSBmp));

    BitBlt(SDC, 0, 0, width, height, DC, X, Y, SRCCOPY);
    unsigned int data_size = ((width * BitsPerPixel + 31) / 32) * 4 * height;
    std::vector<std::uint8_t> Data(data_size);
    this->Pixels.resize(data_size);

    BITMAPINFO Info = {sizeof(BITMAPINFOHEADER), static_cast<long>(width), static_cast<long>(height), 1, BitsPerPixel, BI_RGB, data_size, 0, 0, 0, 0};
    GetDIBits(SDC, hSBmp, 0, height, &Data[0], &Info, DIB_RGB_COLORS);
    this->Flip(&Data[0], &Pixels[0], width, height, BitsPerPixel);

    DeleteDC(SDC);
    DeleteObject(hSBmp);
    ReleaseDC(nullptr, MemDC);
}
#endif

int main()
{
    #if defined _WIN32 || defined _WIN64
    HWND SomeWindowHandle = GetDesktopWindow();
    HDC DC = GetDC(SomeWindowHandle);

    Image Img = Image(DC, 0, 0, 200, 200); //screenshot of 0, 0, 200, 200..

    ReleaseDC(SomeWindowHandle, DC);
    #else
    Image Img = Image(some_pixel_pointer, 200, 200); //pointer to pixels..
    #endif

    std::unique_ptr<tesseract::TessBaseAPI> tesseract_ptr(new tesseract::TessBaseAPI());

    tesseract_ptr->Init("/tesseract/tessdata', 'eng");
    tesseract_ptr->SetImage(Img.GetPixels(), Img.GetWidth(), Img.GetHeight(), Img.GetBytesPerPixel(), Img.GetBytesPerScanLine()); //Fixed this line..

    std::unique_ptr<char[]> utf8_text_ptr(tesseract_ptr->GetUTF8Text());

    std::cout<<utf8_text_ptr.get()<<"\n";

    return 0;
}

Answer 2

你可以在Windows上这样做。

#include <tesseract/capi.h>
#include <windows.h>

void ReadFromScreen(RECT rc)
{
    HWND hWndDesktop = GetDesktopWindow();
    HDC hDC = GetDC(hWndDesktop);

#define BITS_PER_PIXEL   32
#define BYTES_PER_PIXEL  (BITS_PER_PIXEL / 8)
    int nWidth = rc.right - rc.left;
    int nHeight = rc.bottom - rc.top;
    BITMAPINFO bi;
    memset(&bi, 0, sizeof(bi));
    bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bi.bmiHeader.biWidth = nWidth;
    bi.bmiHeader.biHeight = -nHeight;
    bi.bmiHeader.biPlanes = 1;
    bi.bmiHeader.biBitCount = BITS_PER_PIXEL;
    bi.bmiHeader.biCompression = BI_RGB;

    void* pixels;
    HBITMAP hBitmap = ::CreateDIBSection(0, &bi, DIB_RGB_COLORS, &pixels, NULL, 0);
    HDC hMemDC = CreateCompatibleDC(NULL);
    SelectObject(hMemDC, hBitmap);
    BitBlt(hMemDC, 0, 0, nWidth, nHeight, hDC, rc.left, rc.top, SRCCOPY);
    int nDataSize = nWidth * nHeight * BYTES_PER_PIXEL;
    TessBaseAPISetImage(pTessBaseAPI, (const unsigned char*)pixels, nWidth, nHeight, BYTES_PER_PIXEL, BYTES_PER_PIXEL * nWidth);
    if (TessBaseAPIRecognize(pTessBaseAPI, NULL) != 0)
    {
        return;
    }
    char* szText = TessBaseAPIGetUTF8Text(pTessBaseAPI);
    // Todo something with szText

    TessDeleteText(szText);
    DeleteObject(hBitmap);
    DeleteDC(hMemDC);
}