libTIFF 图像读取与保存

本系列文章由 @YhL_Leo 出品，转载请注明出处。

文章链接： http://blog.csdn.net/YhL_Leo/article/details/49848391

1 头文件

libtiff定义一系列C语言类型的数据结构，调用时包含的头文件为：

#include "tiffio.h"

2 文件读写

/* read from an existing TIFF image */

void main()

{

    TIFF* tif = TIFFOpen("foo.tif", "r");

    ... do stuff ...

    TIFFClose(tif);  // or TIFFFlush(tif);

}

/* create or overwrite a TIFF image */

void main()

{

    TIFF* tif = TIFFOpen("foo.tif", "w");

    ... do stuff ...

    TIFFClose(tif);  // or TIFFFlush(tif);

}

不同于stdio library对TIFF文件的操作可以同时支持读和写，libtiff对于TIFF文件的操作模式是不可变更的，也就是说对一个指定的TIFF文件，一次只能支持对文件的读或写中的一种操作。

3 多目录文件读写

TIFF格式支持将多个图像文件存储为一个文件的功能，每个图片都有一个对应的数据结构称为一个目录，其中包括全部的信息格式和图像数据内容。图像之间可以是相关的也可以使不相关的。

#include "tiffio.h"

int main(int argc, char* argv[])

{

    TIFF* tif = TIFFOpen(argv[1], "r");

    if (tif)

    {

        int dircount = 0;

        do {

            dircount++;

        } while (TIFFReadDirectory(tif));

        printf("%d directories in %s\n", dircount, argv[1]);

        TIFFClose(tif);

    }

    return 0;

}

// write: TIFFWriteDirectory()

4 标签读取与设置

图像相关的信息例如宽、高、通道数、定向信息、颜色信息等。libtiff中提供了获取和设置标签值的函数：TIFFGetField和TIFFSetField：

/* read the tags */

uint32 width, height;

uint16 ncn;

TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &width);    // image width in pixels

TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &height);  // image height in pixels

TIFFGetField(tif, TIFFTAG_SAMPLESPERPIXEL, &ncn); // samples per pixel -> channels

cout << width << " " << height << " " << ncn << endl; 

/* set the tags */

TIFFSetField( imageWrite, TIFFTAG_IMAGEWIDTH, width );

TIFFSetField( imageWrite, TIFFTAG_IMAGELENGTH, height );

TIFFSetField( imageWrite, TIFFTAG_BITSPERSAMPLE, 8);    // 8 bits per channel

TIFFSetField( imageWrite, TIFFTAG_SAMPLESPERPIXEL, 4);  // 4 channels

下面列出几种常用的TIFF图像信息标签：

#define TIFFTAG_IMAGEWIDTH        256   /* image width in pixels */

#define TIFFTAG_IMAGELENGTH       257   /* image height in pixels */

#define TIFFTAG_BITSPERSAMPLE     258   /* bits per channel (sample) */

#define TIFFTAG_SAMPLESPERPIXEL   277   /* samples per pixel */

#define TIFFTAG_COMPRESSION       259   /* data compression technique */

#define TIFFTAG_PHOTOMETRIC       262   /* photometric interpretation */

#define TIFFTAG_PLANARCONFIG      284   /* storage organization */

#define TIFFTAG_XRESOLUTION       282   /* pixels/resolution in x */

#define TIFFTAG_YRESOLUTION       283   /* pixels/resolution in y */

#define TIFFTAG_RESOLUTIONUNIT    296   /* units of resolutions */

5 RGBA 图像读取与存储

对于4通道的图像，libtiff提供的数据颜色顺序为A B G R，并且整合为32-bit无符号整型数据（每个通道为8 bits），数据读取方法为使用TIFFReadRGBAImage函数：

#include "tiffio.h"

// first method: TIFFReadRGBAImage

int main(int argc, char* argv[])

{

    TIFF* tif = TIFFOpen(argv[1], "r");

    if (tif) {

    uint32 w, h;

    size_t npixels;

    uint32* raster;

    TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &w);

    TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &h);

    npixels = w * h;

    raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));

    if (raster != NULL) {

        if (TIFFReadRGBAImage(tif, w, h, raster, 0)) {

        ...process raster data...

        }

        _TIFFfree(raster);

    }

    TIFFClose(tif);

    }

    return 0;

}

// second method: TIFFRGBAImageBegin & TIFFRGBAImageGet

int main(int argc, char* argv[])

{

    TIFF* tif = TIFFOpen(argv[1], "r");

    if (tif) {

    TIFFRGBAImage img;

    char emsg[1024];

    if (TIFFRGBAImageBegin(&img, tif, 0, emsg)) {

        size_t npixels;

        uint32* raster;

        npixels = img.width * img.height;

        raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));

        if (raster != NULL) {

        if (TIFFRGBAImageGet(&img, raster, img.width, img.height)) {

            ...process raster data...

        }

        _TIFFfree(raster);

        }

        TIFFRGBAImageEnd(&img);

    } else

        TIFFError(argv[1], emsg);

    TIFFClose(tif);

    }

    return 0;

}

以TIFFReadRGBAImage为例，读取图像后，获得其某一通道的结果，可使用：

// image channel read order : A B G R

if ( TIFFReadRGBAImage(tif, width, height, raster, 0) )

{

    BYTE *imageR = new BYTE[nPixels];

    // image pixels are in an inverted order, which is same as bmp format

    uint32* rowPoint2Src = raster + (height-1)*width;

    BYTE *rowPointerToR  = imageR;

    for ( int rows = height-1; rows >= 0; --rows )

    {

        uint32 *colPoint2Src = rowPoint2Src;

        BYTE* colPoint2R = rowPointerToR;

        for ( int cols = 0; cols < width; cols ++ )

        {

            // read the channel : A

            *colPoint2R = (BYTE)TIFFGetA(*colPoint2Src);

            // or : colPoint2R[0] = (BYTE)TIFFGetA(colPoint2Src[0]);

            colPoint2R++;

            colPoint2Src++;

        }

        rowPoint2Src  -= width;

        rowPointerToR += width;

    }

    cv::Mat imageR_mat( height, width, CV_8UC1, imageR, width );

    imwrite("E:\\0-Alpha.jpg", imageR_mat);

    _TIFFfree(imageR);

}

如果想把4通道TIFF文件，读入内存后转为Mat格式，可以这么做：

/* save as a Mat */

cv::Mat image(height, width, CV_8UC4, cv::Scalar::all(0));

if ( TIFFReadRGBAImage(tif, width, height, raster, 0) )

{

    uchar* imageData = (uchar*)image.data;

    uint32* rowPoint2Src = raster + (height-1)*width;

    for ( int rows = height-1; rows >= 0; --rows )

    {

        uint32 *colPoint2Src = rowPoint2Src;

        // image pixels are in an inverted order, which is same as bmp format

        uchar* colPoint = image.ptr<uchar>( height - rows - 1 );

        for ( int cols = 0; cols < width; cols ++ )

        {

            *colPoint++ = (uchar)TIFFGetB(*colPoint2Src); // B

            *colPoint++ = (uchar)TIFFGetG(*colPoint2Src); // G

            *colPoint++ = (uchar)TIFFGetR(*colPoint2Src); // R

            *colPoint++ = (uchar)TIFFGetA(*colPoint2Src); // A

            colPoint2Src++;

        }

        rowPoint2Src  -= width;

    }

}

创建并保存4通道TIFF图像可以按照下面的方法：

/* creat and write a ABGR tiff image */

#include <iostream>

#include <vector>

#include "cv.h"

#include "highgui.h"

#include "tiffio.h"

using namespace std;

using namespace cv;

void main()

{

    cv::Mat imageGray  = cv::imread( "C:\\Users\\Leo\\Desktop\\Test\\0.jpg" );

    cv::Mat imageAlpha = cv::imread( "C:\\Users\\Leo\\Desktop\\Test\\0-R.jpg" ); 

    if ( imageGray.channels() == 3 )

        cv::cvtColor( imageGray, imageGray, CV_RGB2GRAY );

    if ( imageAlpha.channels() == 3 )

        cv::cvtColor( imageAlpha, imageAlpha, CV_RGB2GRAY );

    int cols = imageGray.cols;

    int rows = imageGray.rows;

    cv::Mat imageMerged(rows, cols, CV_8UC4, cv::Scalar::all(0));

    uchar* data        = (uchar*) imageMerged.data;

    uchar* data_gray   = (uchar*) imageGray.data;

    uchar* data_alpha  = (uchar*) imageAlpha.data;

    for ( int i=0; i<rows; i++ )

    {

        for ( int j=0; j<cols; j++ )

        {

            int index = i*cols + j;

            data[index*4]   = data_gray[index];

            data[index*4+1] = data_gray[index];

            data[index*4+2] = data_gray[index];

            data[index*4+3] = data_alpha[index];

        }

    }

    uint32 width, height;

    width  = cols;

    height = rows;

    /* save as PNG */

    std::vector<int> compression_params;

    compression_params.push_back(CV_IMWRITE_PNG_COMPRESSION);

    compression_params.push_back(9);

    cv::imwrite( "C:\\Users\\Leo\\Desktop\\Test\\0-1.png", imageMerged, compression_params );

    /* save as TIFF */

    TIFF *imageWrite =  TIFFOpen( "C:\\Users\\Leo\\Desktop\\Test\\0-2.tif", "w" );

    if ( imageWrite )

    {

        TIFFSetField( imageWrite, TIFFTAG_IMAGEWIDTH, width );

        TIFFSetField( imageWrite, TIFFTAG_IMAGELENGTH, height );

        TIFFSetField( imageWrite, TIFFTAG_COMPRESSION, COMPRESSION_PACKBITS);

        TIFFSetField( imageWrite, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);

        TIFFSetField( imageWrite, TIFFTAG_PHOTOMETRIC, PHOTOMETRIC_RGB);

        TIFFSetField( imageWrite, TIFFTAG_BITSPERSAMPLE, 8);

        TIFFSetField( imageWrite, TIFFTAG_SAMPLESPERPIXEL, 4);

        uchar *bits = (uchar*) imageMerged.data;

//        uchar* pdst = new uchar[cols*4];

        for ( int i=0; i<rows; i++ )

        {

//             int curidx_bit = i * cols * 4;

//             for ( int idx = 0; idx < cols; idx ++ )

//             {

//                 int curidx_dst  = idx * 4;

//                 int curidx_bit2 = curidx_bit + curidx_dst;

//

//                 pdst[curidx_dst]   = bits[curidx_bit2];

//                 pdst[curidx_dst+1] = bits[curidx_bit2+1];

//                 pdst[curidx_dst+2] = bits[curidx_bit2+2];

//                 pdst[curidx_dst+3] = bits[curidx_bit2+3];

//             }

            TIFFWriteScanline( imageWrite, &bits[i*cols*4], i, 0 );

//            TIFFWriteScanline( imageWrite, pdst, i, 0 );

        }

        TIFFClose( imageWrite );

    }

    else

    {

        std::cout << "Open file error!" << std::endl;

        exit(1);

    }

}

这段代码读取了两张图像，一张为灰度图，另一张为对应的Alpha通道图像，然后将其转换为RGBA图像。代码里给出了TIFFWriteScanline写TIFF的两种方法，其中注释掉的部分即为另一种方法。

6 三种图像I/O读写方法

libTIFF中提供了三种文件读写方式：

Scanline-based
Strip-oriented
Tile-oriented

此处不做过的介绍，详情请阅读 Using The TIFF Library~

Opencv中也有对TIFF文件的操作，也是基于libTIFF库，详情参考文件：grfmt_tiff.cpp。

PS: