TIFFでサムネイル（libtiff）を持つSub IFDを作成

Question

サムネイルにはサムネイルを作成してサブIDFに配置するコードがいくつかありますが、そのコードにはサムネイル、コントラストカーブを適用するなど）、サムネイルを書き込むだけでは難しいです。 Googleには何の助けもありませんでした。

出力ファイルを開いてTIFF *を作成した後で、私のサムネイルデータはすべて準備ができています（私の主な画像データもあります）。どうすればそのように追加できますか？サムネイルは、メイン画像IFDのサブIFD内にあるか？

Answer 1

だからしばらくのlibtiffのソースコードを周り掘り後、私はtif_dirwrite.cでこれに出くわし：

/* 
* Copyright (c) 1988-1997 Sam Leffler 
* Copyright (c) 1991-1997 Silicon Graphics, Inc. 
* 
* Permission to use, copy, modify, distribute, and sell this software and 
* its documentation for any purpose is hereby granted without fee, provided 
* that (i) the above copyright notices and this permission notice appear in 
* all copies of the software and related documentation, and (ii) the names of 
* Sam Leffler and Silicon Graphics may not be used in any advertising or 
* publicity relating to the software without the specific, prior written 
* permission of Sam Leffler and Silicon Graphics. 
*/ 

... 
if (!n) 
    return(0); 
/* 
* Total hack: if this directory includes a SubIFD 
* tag then force the next <n> directories to be 
* written as ``sub directories'' of this one. This 
* is used to write things like thumbnails and 
* image masks that one wants to keep out of the 
* normal directory linkage access mechanism. 
*/ 
tif->tif_flags|=TIFF_INSUBIFD; 
tif->tif_nsubifd=tif->tif_dir.td_nsubifd; 
if (tif->tif_dir.td_nsubifd==1) 
    tif->tif_subifdoff=0; 
else 
    tif->tif_subifdoff=m; 
return(1); 
... 

私はときに持っていたかどうかわからなかったので、（私は著作権情報が含まれてここでは、ライブラリ）からコードを投稿すること

ので

、自分の質問に答えるために（どのようにメイン画像のサブIFD IFD）にサムネイルを書き込む：

//... 
//For the sake of this demo we will assume that I have opened a 
//TIFF (TIFF* created_TIFF) in write mode and have included the correct header 
//files 

//set all of your TIFF fields for the main image 
//... 

//Define the number of sub-IFDs you are going to write 
//(assuming here that we are only writing one thumbnail for the image): 
int number_of_sub_IFDs = 1; 
toff_t sub_IFDs_offsets[1] = { 0UL }; 

//set the TIFFTAG_SUBIFD field: 
if(!TIFFSetField(created_TIFF, TIFFTAG_SUBIFD, number_of_sub_IFDs, 
    sub_IFDs_offsets)) 
{ 
    //there was an error setting the field 
} 

//Write your main image raster data to the TIFF (using whatever means you need, 
//such as TIFFWriteRawStrip, TIFFWriteEncodedStrip, TIFFWriteEncodedTile, etc.) 
//... 

//Write your main IFD like so: 
TIFFWriteDirectory(created_TIFF); 

//Now here is the trick: like the comment in the libtiff source states, the 
//next n directories written will be sub-IFDs of the main IFD (where n is 
//number_of_sub_IFDs specified when you set the TIFFTAG_SUBIFD field) 

//Set up your sub-IFD 
if(!TIFFSetField(created_TIFF, TIFFTAG_SUBFILETYPE, FILETYPE_REDUCEDIMAGE)) 
{ 
    //there was an error setting the field 
} 

//set the rest of the required tags here, as well as any extras you would like 
//(remember, these refer to the thumbnail, not the main image) 
//... 

//Write this sub-IFD: 
TIFFWriteDirectory(created_TIFF); 

//Assuming you are only writing one sub-IFD and are done with the file, you 
//can close it now. If you specified more than one sub-IFD, you need repeat 
//the above code (starting where we set TIFFTAG_SUBFILETYPE) for each of your 
//sub-IFDs 
TIFFClose(created_TIFF); 

私はことを願っていますこれは誰かを助け、私はこれを行う方法を理解するために多くの努力を費やす必要はありません。本当に残念ですが、libtiffはそれがどれほど広く使われているかを考慮すると、それほど文書化されていません。