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:
