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

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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
", 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:

• LibTIFF (libtiff.org)
• LibTIFF (remotesensing.org)
• TIFF Documentation