BMP Format
BMP Format
BMP Format
Prerequites
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NOTHING
What is BMP Format
1. What is BMP Format?
File has format that depends on extension.
1. Sequence of BMP Format?
I will analyze above the image.
1-1. File Header
14 bytes
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42 4D / 62 09 01 00 / 00 00 / 00 00 / 8A 00 00 00
struct BMPFileHeader
{
uint16_t bfType; // 0x4D42
uint32_t bfSize; // 0x00010962
uint16_t bfReserved1; // 0x0000
uint16_t bfReserved2; // 0x0000
uint32_t bfOffBits; // 0x0000008A
};
- First 2 btyes is about extension-type like bmp. jpg. png …
- Next 4 btyes is about file size.
- Next 2 btyes is
- Next 2 btyes is
- Next 4 btyes is about offest where the first pixel is located on the file.
2-2. Info Header
40 bytes
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7C 00 00 00 \
96 00 00 00 \
96 00 00 00 \
01 00 \
18 00 \
00 00 00 00 \
D8 08 01 00 \
00 00 00 00 \
00 00 00 00 \
00 00 00 00 \
00 00 00 00
struct BMPInfoHeader
{
uint32_t biSize; // 0x0000007C
int32_t biWidth; // 0x00000096
int32_t biHeight; // 0x00000096
uint16_t biPlanes; // 0x0001
uint16_t biBitCount; // 0x0018
uint32_t biCompression; // 0x0000
uint32_t biSizeImage; // 0x000108D8
int32_t biXPelsPerMeter; // 0x00000000
int32_t biYPelsPerMeter; // 0x00000000
uint32_t biClrUsed; // 0x00000000
uint32_t biClrImportant; // 0x00000000
};
- First 4 btyes is BITMAPV5HEADER size
- Next 4 btyes is image width
- Next 2 btyes is image height
- Next 2 btyes is
- Next 2 btyes is bit count (RGB 3 bytes per pixel)
- Next 4 btyes is compression
- Next 4 btyes is size of image
- Next 4 btyes is usually 0
- Next 4 btyes is usually 0
- Next 4 btyes is usually 0
- Next 4 btyes is usually 0
2-3. Color Information (Optional)
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// Color Mask
00 00 FF 00 \
00 FF 00 00 \
FF 00 00 00 \
00 00 00 FF \
// Color Table
42 47 52 73 \
8F C2 F5 28 \
51 B8 1E 15 \
1E 85 EB 01 \
33 33 33 13 \
66 66 66 26 \
66 66 66 06 \
99 99 99 09 \
3D 0A D7 03 \
28 5C 8F 32 \
// Color Management
00 00 00 00 \
00 00 00 00 \
00 00 00 00 \
04 00 00 00 \
00 00 00 00 \
00 00 00 00 \
00 00 00 00
struct BMPColorInformation
{
uint32_t bV5RedMask; // 0x00FF0000
uint32_t bV5GreenMask; // 0x0000FF00
uint32_t bV5BlueMask; // 0x000000FF
uint32_t bV5AlphaMask; // 0xFF000000
uint32_t bV5CSType; // 0x73524742
int32_t bV5Endpoints[9];
// 0x28F5C28F 0x151EB851 0x01EB851E 0x13333333
// 0x26666666 0x06666666 0x09999999 0x03D70A3D 0x328F5C28}
uint32_t bV5GammaRed; // 0x00000000
uint32_t bV5GammaGreen; // 0x00000000
uint32_t bV5GammaBlue; // 0x00000000
uint32_t bV5Intent; // 0x00000004
uint32_t bV5ProfileData; // 0x00000000
uint32_t bV5ProfileSize; // 0x00000000
uint32_t bV5Reserved; // 0x00000000
}
2-4. Pixel Data
[B G R B G R B ….]
BMP file is fundamental format. The file do not usually have any compression.
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#include <iostream>
#pragma pack(push,1)
struct sBMPFileHeader
{
uint16_t u16Type;
uint32_t u32Size;
uint16_t u16Reserved1;
uint16_t u16Reserved2;
uint32_t u32OffBits;
};
struct sBMPInfoHeader
{
uint32_t u32Size;
int32_t i32Width;
int32_t i32Height;
uint16_t u16Planes;
uint16_t u16BitCount;
uint32_t u32Compression;
uint32_t u32SizeImage;
int32_t i32XPelsPerMeter;
int32_t i32YPelsPerMeter;
uint32_t u32ClrUsed;
uint32_t u32ClrImportant;
};
#pragma pack(pop)
class CImage
{
public:
CImage()
{
i32Width = 0;
i32Height = 0;
i32BytesPerPixel = 0;
i32Stride = 0;
pU8Buffer = nullptr;
}
~CImage()
{
if (pU8Buffer)
{
free(pU8Buffer);
pU8Buffer = nullptr;
}
}
public:
int i32Width;
int i32Height;
int i32BytesPerPixel;
int i32Stride;
uint8_t* pU8Buffer;
};
enum EFileStatus
{
EFileStatus_OK = 0,
EFileStatus_Unknown = 1,
EFileStatus_NullPointer = 2,
EFileStatus_FailedtoOpen = 3,
EFileStatus_FailedtoClose = 4,
EFileStatus_FailedtoRead = 5,
EFileStatus_FailedtoWrite = 6,
EFileStatus_WrongFormat = 7,
};
EFileStatus LoadBMP(const char* filePath, CImage* pImgOutput)
{
EFileStatus eFileProcess = EFileStatus_Unknown;
FILE* fpImage = nullptr;
do
{
if (!pImgOutput)
break;
fopen_s(&fpImage, filePath, "rb");
if (!fpImage)
{
eFileProcess = EFileStatus_FailedtoOpen;
break;
}
sBMPFileHeader sFileHeader;
{
if (!fread(&sFileHeader, sizeof(sBMPFileHeader), 1, fpImage))
{
eFileProcess = EFileStatus_FailedtoRead;
break;
}
if (sFileHeader.u16Type != 0x4D42)
{
eFileProcess = EFileStatus_WrongFormat;
break;
}
}
sBMPInfoHeader sInfoHeader;
{
if (!fread(&sInfoHeader, sizeof(sBMPInfoHeader), 1, fpImage))
{
eFileProcess = EFileStatus_FailedtoRead;
break;
}
if (sInfoHeader.u16BitCount != 24 && sInfoHeader.u16BitCount != 32)
{
eFileProcess = EFileStatus_WrongFormat;
break;
}
}
if(fseek(fpImage, sFileHeader.u32OffBits, SEEK_SET))
{
eFileProcess = EFileStatus_FailedtoRead;
break;
}
int32_t i32Width = sInfoHeader.i32Width;
int32_t i32Height = sInfoHeader.i32Height;
int32_t i32BytesPerPixel = sInfoHeader.u16BitCount / 8;
int32_t i32Stride = (i32Width * i32BytesPerPixel + 3) & (~3);
int32_t i32BufferSize = i32Stride * i32Height * sizeof(uint8_t);
uint8_t* pU8Buffer = (uint8_t*)malloc(i32BufferSize);
if(!fread(pU8Buffer, i32BufferSize, 1, fpImage))
{
eFileProcess = EFileStatus_FailedtoRead;
break;
}
if (pImgOutput->pU8Buffer)
{
free(pImgOutput->pU8Buffer);
pImgOutput->pU8Buffer = nullptr;
}
pImgOutput->i32Width = i32Width;
pImgOutput->i32Height = i32Height;
pImgOutput->i32BytesPerPixel = i32BytesPerPixel;
pImgOutput->i32Stride = i32Stride;
pImgOutput->pU8Buffer = pU8Buffer;
eFileProcess = EFileStatus_OK;
}
while (false);
if (fpImage)
{
fclose(fpImage);
fpImage = nullptr;
}
return eFileProcess;
}
This post is licensed under CC BY 4.0 by the author.