最近在用blackmagic design (BMD) 的相機(jī)做開發(fā)，用MediaExpress保存的圖片是tga格式的田柔。Matlab和OpenCV都不支持俐巴。
搜了一下，stackoverflow上有個帖子[1]貼了段代碼：
#include <vector>
#include <fstream>
#ifdef __APPLE__
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#endif
#ifdef _WIN32
#include <GL/gl.h>
#include <GL/glu.h>
#endif
typedef union PixelInfo
{
std::uint32_t Colour;
struct
{
std::uint8_t R, G, B, A;
};
} *PPixelInfo;
class Tga
{
private:
std::vector<std::uint8_t> Pixels;
bool ImageCompressed;
std::uint32_t width, height, size, BitsPerPixel;
public:
Tga(const char* FilePath);
std::vector<std::uint8_t> GetPixels() {return this->Pixels;}
std::uint32_t GetWidth() const {return this->width;}
std::uint32_t GetHeight() const {return this->height;}
bool HasAlphaChannel() {return BitsPerPixel == 32;}
};
Tga::Tga(const char* FilePath)
{
std::fstream hFile(FilePath, std::ios::in | std::ios::binary);
if (!hFile.is_open()){throw std::invalid_argument("File Not Found.");}
std::uint8_t Header[18] = {0};
std::vector<std::uint8_t> ImageData;
static std::uint8_t DeCompressed[12] = {0x0, 0x0, 0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
static std::uint8_t IsCompressed[12] = {0x0, 0x0, 0xA, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
hFile.read(reinterpret_cast<char*>(&Header), sizeof(Header));
if (!std::memcmp(DeCompressed, &Header, sizeof(DeCompressed)))
{
BitsPerPixel = Header[16];
width = Header[13] * 256 + Header[12];
height = Header[15] * 256 + Header[14];
size = ((width * BitsPerPixel + 31) / 32) * 4 * height;
if ((BitsPerPixel != 24) && (BitsPerPixel != 32))
{
hFile.close();
throw std::invalid_argument("Invalid File Format. Required: 24 or 32 Bit Image.");
}
ImageData.resize(size);
ImageCompressed = false;
hFile.read(reinterpret_cast<char*>(ImageData.data()), size);
}
else if (!std::memcmp(IsCompressed, &Header, sizeof(IsCompressed)))
{
BitsPerPixel = Header[16];
width = Header[13] * 256 + Header[12];
height = Header[15] * 256 + Header[14];
size = ((width * BitsPerPixel + 31) / 32) * 4 * height;
if ((BitsPerPixel != 24) && (BitsPerPixel != 32))
{
hFile.close();
throw std::invalid_argument("Invalid File Format. Required: 24 or 32 Bit Image.");
}
PixelInfo Pixel = {0};
int CurrentByte = 0;
std::size_t CurrentPixel = 0;
ImageCompressed = true;
std::uint8_t ChunkHeader = {0};
int BytesPerPixel = (BitsPerPixel / 8);
ImageData.resize(width * height * sizeof(PixelInfo));
do
{
hFile.read(reinterpret_cast<char*>(&ChunkHeader), sizeof(ChunkHeader));
if(ChunkHeader < 128)
{
++ChunkHeader;
for(int I = 0; I < ChunkHeader; ++I, ++CurrentPixel)
{
hFile.read(reinterpret_cast<char*>(&Pixel), BytesPerPixel);
ImageData[CurrentByte++] = Pixel.B;
ImageData[CurrentByte++] = Pixel.G;
ImageData[CurrentByte++] = Pixel.R;
if (BitsPerPixel > 24) ImageData[CurrentByte++] = Pixel.A;
}
}
else
{
ChunkHeader -= 127;
hFile.read(reinterpret_cast<char*>(&Pixel), BytesPerPixel);
for(int I = 0; I < ChunkHeader; ++I, ++CurrentPixel)
{
ImageData[CurrentByte++] = Pixel.B;
ImageData[CurrentByte++] = Pixel.G;
ImageData[CurrentByte++] = Pixel.R;
if (BitsPerPixel > 24) ImageData[CurrentByte++] = Pixel.A;
}
}
} while(CurrentPixel < (width * height));
}
else
{
hFile.close();
throw std::invalid_argument("Invalid File Format. Required: 24 or 32 Bit TGA File.");
}
hFile.close();
this->Pixels = ImageData;
}
int main()
{
Tga info = Tga("C:/Users/...../Desktop/SomeTGA.tga");
GLuint texture = 0;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, info.HasAlphaChannel() ? GL_RGBA : GL_RGB, info.GetWidth(), info.GetWidth(), 0, info.HasAlphaChannel() ? GL_RGBA : GL_RGB, GL_UNSIGNED_BYTE, info.GetPixels().data());
}
這段功能完整的代碼可以直接運(yùn)行凯楔，代碼寫的也通暢窜骄。
但是我將從BMD相機(jī)得到tga作為輸入，代碼卻拋出異常："Invalid File Format. Required: 24 or 32 Bit TGA File.
循著源代碼排查了一下摆屯，在tga的格式檢查步驟中邻遏，代碼認(rèn)為給出了我輸入的tga格式的圖片不符合它的要求糠亩。
這就有點(diǎn)奇怪，于是查一下tga的標(biāo)準(zhǔn)的一個實現(xiàn)描述[2], 發(fā)現(xiàn)stack overflow給出的代碼是符合這個tga的實現(xiàn)的准验。
既然如此赎线，那可能是我的TGA文件有點(diǎn)不一樣。于是只好用二進(jìn)制的方式打開我的tga圖片糊饱。
發(fā)現(xiàn)第一個字節(jié)就是0xe垂寥，跟標(biāo)準(zhǔn)給出的0x0不一樣。另外另锋，header的長度為32個字節(jié)滞项，不是18個字節(jié)。
這兩個地方改了一下夭坪，tga文件就可以被讀入內(nèi)存了文判。
能跑的Tga類如下：
typedef union PixelInfo
{
std::uint32_t Colour;
struct
{
std::uint8_t R, G, B, A;
};
} *PPixelInfo;
class Tga
{
private:
std::vector<std::uint8_t> Pixels;
bool ImageCompressed;
std::uint32_t width, height, size, BitsPerPixel;
public:
Tga(const char* FilePath);
std::vector<std::uint8_t> GetPixels() {return this->Pixels;}
std::uint32_t GetWidth() const {return this->width;}
std::uint32_t GetHeight() const {return this->height;}
bool HasAlphaChannel() {return BitsPerPixel == 32;}
};
Tga::Tga(const char* FilePath)
{
std::fstream hFile(FilePath, std::ios::in | std::ios::binary);
if (!hFile.is_open()){throw std::invalid_argument("File Not Found.");}
std::uint8_t Header[32] = {0};
std::vector<std::uint8_t> ImageData;
static std::uint8_t DeCompressed[12] = {0xe, 0x0, 0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
static std::uint8_t IsCompressed[12] = {0x0, 0x0, 0xA, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0};
hFile.read(reinterpret_cast<char*>(&Header), sizeof(Header));
if (!std::memcmp(DeCompressed, &Header, sizeof(DeCompressed)))
{
BitsPerPixel = Header[16];
width = Header[13] * 256 + Header[12];
height = Header[15] * 256 + Header[14];
size = ((width * BitsPerPixel + 31) / 32) * 4 * height;
if ((BitsPerPixel != 24) && (BitsPerPixel != 32))
{
hFile.close();
throw std::invalid_argument("Invalid File Format. Required: 24 or 32 Bit Image.");
}
ImageData.resize(size);
ImageCompressed = false;
hFile.read(reinterpret_cast<char*>(ImageData.data()), size);
}
else if (!std::memcmp(IsCompressed, &Header, sizeof(IsCompressed)))
{
BitsPerPixel = Header[16];
width = Header[13] * 256 + Header[12];
height = Header[15] * 256 + Header[14];
size = ((width * BitsPerPixel + 31) / 32) * 4 * height;
if ((BitsPerPixel != 24) && (BitsPerPixel != 32))
{
hFile.close();
throw std::invalid_argument("Invalid File Format. Required: 24 or 32 Bit Image.");
}
PixelInfo Pixel = {0};
int CurrentByte = 0;
std::size_t CurrentPixel = 0;
ImageCompressed = true;
std::uint8_t ChunkHeader = {0};
int BytesPerPixel = (BitsPerPixel / 8);
ImageData.resize(width * height * sizeof(PixelInfo));
do
{
hFile.read(reinterpret_cast<char*>(&ChunkHeader), sizeof(ChunkHeader));
if(ChunkHeader < 128)
{
++ChunkHeader;
for(int I = 0; I < ChunkHeader; ++I, ++CurrentPixel)
{
hFile.read(reinterpret_cast<char*>(&Pixel), BytesPerPixel);
ImageData[CurrentByte++] = Pixel.B;
ImageData[CurrentByte++] = Pixel.G;
ImageData[CurrentByte++] = Pixel.R;
if (BitsPerPixel > 24) ImageData[CurrentByte++] = Pixel.A;
}
}
else
{
ChunkHeader -= 127;
hFile.read(reinterpret_cast<char*>(&Pixel), BytesPerPixel);
for(int I = 0; I < ChunkHeader; ++I, ++CurrentPixel)
{
ImageData[CurrentByte++] = Pixel.B;
ImageData[CurrentByte++] = Pixel.G;
ImageData[CurrentByte++] = Pixel.R;
if (BitsPerPixel > 24) ImageData[CurrentByte++] = Pixel.A;
}
}
} while(CurrentPixel < (width * height));
}
else
{
hFile.close();
throw std::invalid_argument("Invalid File Format. Required: 24 or 32 Bit TGA File.");
}
hFile.close();
this->Pixels = ImageData;
}
另外，如果要把內(nèi)存里面的圖片信息放進(jìn)OpenCV里面室梅，用下面的代碼就可以：
Tga tgaImg = Tga("文件的路徑戏仓，比如/home/userA/tmp/test.tga");
Mat img(tgaImg.GetHeight(), tgaImg.GetWidth(), CV_8UC4);
memcpy(img.data, tgaImg.GetPixels().data(), tgaImg.GetHeight() * tgaImg.GetWidth() * 4);
[1]https://stackoverflow.com/questions/20595340/loading-a-tga-bmp-file-in-c-opengl
[2]http://www.paulbourke.net/dataformats/tga/
