BmpImageSupport.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
 
struct FBitmapFileHeader;
struct FBitmapInfoHeader;
 
// Bitmap compression types.
enum EBitmapCompression
{
    BCBI_RGB            = 0,
    BCBI_RLE8           = 1,
    BCBI_RLE4           = 2,
    BCBI_BITFIELDS      = 3,
    BCBI_JPEG           = 4,
    BCBI_PNG            = 5,
    BCBI_ALPHABITFIELDS = 6,
};
 
// Bitmap info header versions.
enum class EBitmapHeaderVersion : uint8
{
    BHV_BITMAPINFOHEADER   = 0,
    BHV_BITMAPV2INFOHEADER = 1,
    BHV_BITMAPV3INFOHEADER = 2,
    BHV_BITMAPV4HEADER     = 3,
    BHV_BITMAPV5HEADER     = 4,
    BHV_INVALID = 0xFF
};
 
// Color space type of the bitmap, property introduced in Bitmap header version 4.
enum class EBitmapCSType : uint32
{
    BCST_BLCS_CALIBRATED_RGB     = 0x00000000,
    BCST_LCS_sRGB                = 0x73524742,
    BCST_LCS_WINDOWS_COLOR_SPACE = 0x57696E20,
    BCST_PROFILE_LINKED          = 0x4C494E4B,
    BCST_PROFILE_EMBEDDED        = 0x4D424544,
};
 
// .BMP file header.
#pragma pack(push,1)
struct FBitmapFileHeader
{
    uint16 bfType;
    uint32 bfSize;
    uint16 bfReserved1;
    uint16 bfReserved2;
    uint32 bfOffBits;
 
    friend FArchive& operator<<( FArchive& Ar, FBitmapFileHeader& H )
    {
        Ar << H.bfType << H.bfSize << H.bfReserved1 << H.bfReserved2 << H.bfOffBits;
        return Ar;
    }
};
#pragma pack(pop)
 
// .BMP subheader.
#pragma pack(push,1)
struct FBitmapInfoHeader
{
    uint32 biSize;
    uint32 biWidth;
    int32 biHeight;
    uint16 biPlanes;
    uint16 biBitCount;
    uint32 biCompression;
    uint32 biSizeImage;
    uint32 biXPelsPerMeter;
    uint32 biYPelsPerMeter;
    uint32 biClrUsed;
    uint32 biClrImportant;
    friend FArchive& operator<<( FArchive& Ar, FBitmapInfoHeader& H )
    {
        Ar << H.biSize << H.biWidth << H.biHeight;
        Ar << H.biPlanes << H.biBitCount;
        Ar << H.biCompression << H.biSizeImage;
        Ar << H.biXPelsPerMeter << H.biYPelsPerMeter;
        Ar << H.biClrUsed << H.biClrImportant;
        return Ar;
    }
    
public:
    EBitmapHeaderVersion GetHeaderVersion() const
    {
        // Since there is no field indicating the header version of the bitmap in the FileHeader,
        // the only way to know the format version is to check the header size.
        //
        // note that Adobe (incorrectly) writes biSize as 40 and then BMFH bfOffBits will be 52 or 56
        //  so this code does not detect those variant headers
        switch (biSize)
        {
            case 40:
                return EBitmapHeaderVersion::BHV_BITMAPINFOHEADER;
            case 52:
                // + RGB 32 bit masks
                return EBitmapHeaderVersion::BHV_BITMAPV2INFOHEADER;
            case 56:
                // + RGBA 32 bit masks
                return EBitmapHeaderVersion::BHV_BITMAPV3INFOHEADER;
            case 108:
                return EBitmapHeaderVersion::BHV_BITMAPV4HEADER;
            case 124:
                return EBitmapHeaderVersion::BHV_BITMAPV5HEADER;
            default:
                return EBitmapHeaderVersion::BHV_INVALID;
        }
    }
};
#pragma pack(pop)
 
 
// .BMP subheader V4
#pragma pack(push,1)
struct FBitmapInfoHeaderV4
{
    uint32 biSize;
    uint32 biWidth;
    int32 biHeight;
    uint16 biPlanes;
    uint16 biBitCount;
    uint32 biCompression;
    uint32 biSizeImage;
    uint32 biXPelsPerMeter;
    uint32 biYPelsPerMeter;
    uint32 biClrUsed;
    uint32 biClrImportant;
    uint32 biRedMask;
    uint32 biGreenMask;
    uint32 biBlueMask;
    uint32 biAlphaMask;
    uint32 biCSType;
    int32 biEndPointRedX;
    int32 biEndPointRedY;
    int32 bibiEndPointRedZ;
    int32 bibiEndPointGreenX;
    int32 biEndPointGreenY;
    int32 biEndPointGreenZ;
    int32 biEndPointBlueX;
    int32 biEndPointBlueY;
    int32 biEndPointBlueZ;
    uint32 biGammaRed;
    uint32 biGammaGreen;
    uint32 biGammaBlue;
    
    friend FArchive& operator<<(FArchive& Ar, FBitmapInfoHeaderV4& H)
    {
        Ar << H.biSize << H.biWidth << H.biHeight;
        Ar << H.biPlanes << H.biBitCount;
        Ar << H.biCompression << H.biSizeImage;
        Ar << H.biXPelsPerMeter << H.biYPelsPerMeter;
        Ar << H.biClrUsed << H.biClrImportant;
        Ar << H.biRedMask << H.biGreenMask << H.biBlueMask << H.biAlphaMask;
        Ar << H.biCSType << H.biEndPointRedX << H.biEndPointRedY << H.bibiEndPointRedZ;
        Ar << H.bibiEndPointGreenX << H.biEndPointGreenY << H.biEndPointGreenZ;
        Ar << H.biEndPointBlueX << H.biEndPointBlueY << H.biEndPointBlueZ;
        Ar << H.biGammaRed << H.biGammaGreen << H.biGammaBlue;
        return Ar;
    }
};
#pragma pack(pop)
 
 
#pragma pack(push, 1)
//Used by InfoHeaders pre-version 4, a structure that is declared after the FBitmapInfoHeader.
struct FBmiColorsMask
{
    // RGBA, in header pre-version 4, Alpha was only used as padding.
    uint32 RGBAMask[4];
};
#pragma pack(pop)