OpenCV/tesseract：如何用GDI+位图替换libpng、libtiff等（通过GDI+加载到CV::mat中）

Question

因此，如果我动态编译我的项目，我将不得不与我的项目一起交付一堆DLL。如果我静态编译，我会产生一个巨大的输出文件，它会膨胀几兆字节。

这太丑了。我不想那样。

另一个问题是，几乎所有的开源项目--主要是在Linux/Mac世界中开发的--如果在Windows上编译，都不支持Unicode。在内部，它们都将std::string传递给fopen()。在Linux上，使用UTF8编码路径的变通方法可能起作用，但在Windows上就不起作用了。因此日语用户无法打开具有日语名称的文件夹中的图像文件。虽然Microsoft在20世纪90年代初就已经做出了巨大努力，将整个Windows NT操作系统转换为100%兼容Unicode，但20年后的大多数开源项目（如libpng）仍然不支持通过std::wstring传递路径。

// #define HAVE_JASPER
// #define HAVE_JPEG
// #define HAVE_PNG
// #define HAVE_TIFF
etc..

#define  HAVE_LIBJPEG   0
#define  HAVE_LIBTIFF   0
#define  HAVE_LIBPNG    0
#define  HAVE_LIBZ      0
#define  HAVE_LIBGIF    0
#define  HAVE_LIBUNGIF  0
etc..

我知道这可以用几行代码完成，但是OpenCV项目中缺少这样一个有用的完整类。我的第一次试验表明，这并不像第一次看到的那样微不足道，因为需要进行大量的转换。

是否有一个类已经为此目的而制作？

Answer 1

我找不到一个现成的类，所以我写了自己的类：

我希望它对某些人有用，我希望它将作为Windows用户的可选附加组件包含在OpenCV项目中。

优点：

null

#pragma once

#include <gdiplus.h>
#pragma comment(lib, "gdiplus.lib")

// IMPORTANT:
// This must be included AFTER gdiplus !!
// (OpenCV #undefine's min(), max())
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"

using namespace cv;

class CGdiPlus
{
public:
    static void  Init();
    static Mat  ImgRead(const WCHAR* u16_File);
    static void ImgWrite(Mat i_Mat, const WCHAR* u16_File);
    static Mat  CopyBmpToMat(Gdiplus::Bitmap* pi_Bmp);
    static Mat  CopyBmpDataToMat(Gdiplus::BitmapData* pi_Data);
    static Gdiplus::Bitmap* CopyMatToBmp(Mat& i_Mat);

private:
    static CLSID GetEncoderClsid(const WCHAR* u16_File);

    static BOOL mb_InitDone;
};

#include "stdafx.h"
#include "CGdiPlus.h"

using namespace Gdiplus;

BOOL CGdiPlus::mb_InitDone = FALSE;

// Do not call this function in the DLL loader lock!
void CGdiPlus::Init()
{
    if (mb_InitDone)
        return;

    GdiplusStartupInput k_Input;
    ULONG_PTR u32_Token;
    if (Ok != GdiplusStartup(&u32_Token, &k_Input, NULL))
        throw L"Error initializing GDI+";

    mb_InitDone = TRUE;
}

Mat CGdiPlus::CopyBmpToMat(Bitmap* pi_Bmp)
{
    assert(mb_InitDone);

    BitmapData i_Data;
    Gdiplus::Rect k_Rect(0, 0, pi_Bmp->GetWidth(), pi_Bmp->GetHeight());
    if (Ok != pi_Bmp->LockBits(&k_Rect, ImageLockModeRead, pi_Bmp->GetPixelFormat(), &i_Data))
        throw L"Error locking Bitmap.";

    Mat i_Mat = CopyBmpDataToMat(&i_Data);

    pi_Bmp->UnlockBits(&i_Data);
    return i_Mat;
}

Mat CGdiPlus::CopyBmpDataToMat(BitmapData* pi_Data)
{
    assert(mb_InitDone);

    int s32_CvType;
    switch (pi_Data->PixelFormat)
    {
        case PixelFormat1bppIndexed:
        case PixelFormat8bppIndexed:
            // Special case treated separately below
            break;

        case PixelFormat24bppRGB:  // 24 bit
            s32_CvType = CV_8UC3; 
            break;

        case PixelFormat32bppRGB:  // 32 bit
        case PixelFormat32bppARGB: // 32 bit + Alpha channel    
            s32_CvType = CV_8UC4; 
            break; 

        default: 
            throw L"Image format not supported.";
    }

    Mat i_Mat;
    if (pi_Data->PixelFormat == PixelFormat1bppIndexed) // 1 bit (special case)
    {
        i_Mat = Mat(pi_Data->Height, pi_Data->Width, CV_8UC1);

        for (UINT Y=0; Y<pi_Data->Height; Y++)
        {
            BYTE* pu8_Src = (BYTE*)pi_Data->Scan0 + Y * pi_Data->Stride;
            BYTE* pu8_Dst = i_Mat.ptr<BYTE>(Y);

            BYTE u8_Mask = 0x80;
            for (UINT X=0; X<pi_Data->Width; X++)
            {
                pu8_Dst[0] = (pu8_Src[0] & u8_Mask) ? 255 : 0;
                pu8_Dst++;

                u8_Mask >>= 1;
                if (u8_Mask == 0)
                {
                    pu8_Src++;
                    u8_Mask = 0x80;
                }
            }
        }
    }
    else if (pi_Data->PixelFormat == PixelFormat8bppIndexed) // 8 bit gray scale palette (special case)
    {
        i_Mat = Mat(pi_Data->Height, pi_Data->Width, CV_8UC1);

        BYTE* u8_Src = (BYTE*)pi_Data->Scan0;
        BYTE* u8_Dst = i_Mat.data;

        for (UINT R=0; R<pi_Data->Height; R++)
        {
            memcpy(u8_Dst, u8_Src, pi_Data->Width);
            u8_Src += pi_Data->Stride;
            u8_Dst += i_Mat.step;
        }
    }
    else // 24 Bit / 32 Bit
    {
        // Create a Mat pointing to external memory
        Mat i_Ext(pi_Data->Height, pi_Data->Width, s32_CvType, pi_Data->Scan0, pi_Data->Stride);

        // Create a Mat with own memory
        i_Ext.copyTo(i_Mat);
    }
    return i_Mat;
}

Bitmap* CGdiPlus::CopyMatToBmp(Mat& i_Mat)
{
    assert(mb_InitDone);

    PixelFormat e_Format;
    switch (i_Mat.channels())
    {
        case 1: e_Format = PixelFormat8bppIndexed; break;
        case 3: e_Format = PixelFormat24bppRGB;    break;
        case 4: e_Format = PixelFormat32bppARGB;   break;
        default: throw L"Image format not supported.";
    }

    // Create Bitmap with own memory
    Bitmap* pi_Bmp = new Bitmap(i_Mat.cols, i_Mat.rows, e_Format);

    BitmapData i_Data;
    Gdiplus::Rect k_Rect(0, 0, i_Mat.cols, i_Mat.rows);
    if (Ok != pi_Bmp->LockBits(&k_Rect, ImageLockModeWrite, e_Format, &i_Data))
    {
        delete pi_Bmp;
        throw L"Error locking Bitmap.";
    }

    if (i_Mat.elemSize1() == 1) // 1 Byte per channel (8 bit gray scale palette)
    {
        BYTE* u8_Src = i_Mat.data;
        BYTE* u8_Dst = (BYTE*)i_Data.Scan0;

        int s32_RowLen = i_Mat.cols * i_Mat.channels(); // != i_Mat.step !!

        // The Windows Bitmap format requires all rows to be DWORD aligned (always!)
        // while OpenCV by default stores bitmap data sequentially.
        for (int R=0; R<i_Mat.rows; R++)
        {
            memcpy(u8_Dst, u8_Src, s32_RowLen);
            u8_Src += i_Mat.step;    // step may be e.g 3729
            u8_Dst += i_Data.Stride; // while Stride is 3732
        }
    }
    else // i_Mat may contain e.g. float data (CV_32F -> 4 Bytes per pixel grayscale)
    {
        int s32_Type;
        switch (i_Mat.channels())
        {
            case 1: s32_Type = CV_8UC1; break;
            case 3: s32_Type = CV_8UC3; break;
            default: throw L"Image format not supported.";
        }

        CvMat i_Dst;
        cvInitMatHeader(&i_Dst, i_Mat.rows, i_Mat.cols, s32_Type, i_Data.Scan0, i_Data.Stride);

        CvMat i_Img = i_Mat;
        cvConvertImage(&i_Img, &i_Dst, 0);
    }

    pi_Bmp->UnlockBits(&i_Data);

    // Add the grayscale palette if required.
    if (e_Format == PixelFormat8bppIndexed)
    {
        CByteArray i_Arr;
        i_Arr.SetSize(sizeof(ColorPalette) + 256 * sizeof(ARGB));
        ColorPalette* pk_Palette = (ColorPalette*)i_Arr.GetData();

        pk_Palette->Count = 256;
        pk_Palette->Flags = PaletteFlagsGrayScale;

        ARGB* pk_Color = &pk_Palette->Entries[0];
        for (int i=0; i<256; i++)
        {
            pk_Color[i] = Color::MakeARGB(255, i, i, i);
        }

        if (Ok != pi_Bmp->SetPalette(pk_Palette))
        {
            delete pi_Bmp;
            throw L"Error setting grayscale palette.";
        }
    }
    return pi_Bmp;
}

Mat CGdiPlus::ImgRead(const WCHAR* u16_File)
{
    assert(mb_InitDone);

    Bitmap i_Bmp(u16_File);
    if (!i_Bmp.GetWidth() || !i_Bmp.GetHeight())
        throw L"Error loading image from file.";

    return CopyBmpToMat(&i_Bmp);
}

void CGdiPlus::ImgWrite(Mat i_Mat, const WCHAR* u16_File)
{
    assert(mb_InitDone);

    CLSID k_Clsid = GetEncoderClsid(u16_File);

    Bitmap* pi_Bmp = CopyMatToBmp(i_Mat);

    Status e_Status = pi_Bmp->Save(u16_File, &k_Clsid);

    delete pi_Bmp;

    if (e_Status != Ok)
        throw L"Error saving image to file.";
}

// Get the class identifier of the image encoder for the given file extension.
// e.g. {557CF406-1A04-11D3-9A73-0000F81EF32E}  for PNG images
CLSID CGdiPlus::GetEncoderClsid(const WCHAR* u16_File)
{
    assert(mb_InitDone);

    UINT u32_Encoders, u32_Size;
    if (Ok != GetImageEncodersSize(&u32_Encoders, &u32_Size))
        throw L"Error obtaining image encoders size";

    CByteArray i_Arr;
    i_Arr.SetSize(u32_Size);
    ImageCodecInfo* pi_Info = (ImageCodecInfo*)i_Arr.GetData();

    if (Ok != GetImageEncoders(u32_Encoders, u32_Size, pi_Info))
        throw L"Error obtaining image encoders";

    CStringW s_Ext = u16_File;
    int Pos = s_Ext.ReverseFind('.');
    if (Pos < 0)
        throw L"Invalid image filename.";

    // s_Ext = "*.TIF;"
    s_Ext = L"*" + s_Ext.Mid(Pos) + L";";
    s_Ext.MakeUpper();

    // Search the file extension
    for (UINT i=0; i<u32_Encoders; i++)
    {
        CStringW s_Extensions = pi_Info->FilenameExtension;
        s_Extensions += ';';

        // s_Extensions = "*.TIFF;*.TIF;"
        if (s_Extensions.Find(s_Ext) >= 0)
            return pi_Info->Clsid;

        pi_Info ++;
    }

    throw L"No image encoder found for file extension " + s_Ext;
}