最近在用blackmagic design (BMD) 的相机做开发，用MediaExpress保存的图片是tga格式的。Matlab和OpenCV都不支持。
搜了一下，stackoverflow上有个帖子[1]贴了段代码：
#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());
}
这段功能完整的代码可以直接运行，代码写的也通畅。
但是我将从BMD相机得到tga作为输入，代码却抛出异常："Invalid File Format. Required: 24 or 32 Bit TGA File.
循着源代码排查了一下，在tga的格式检查步骤中，代码认为给出了我输入的tga格式的图片不符合它的要求。
这就有点奇怪，于是查一下tga的标准的一个实现描述[2], 发现stack overflow给出的代码是符合这个tga的实现的。
既然如此，那可能是我的TGA文件有点不一样。于是只好用二进制的方式打开我的tga图片。
发现第一个字节就是0xe，跟标准给出的0x0不一样。另外，header的长度为32个字节，不是18个字节。
这两个地方改了一下，tga文件就可以被读入内存了。
能跑的Tga类如下：
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，如果要把内存里面的图片信息放进OpenCV里面，用下面的代码就可以：
Tga tgaImg = Tga("文件的路径，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/
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