2020.02.13 22:23 "[Tiff] Tiff Thumbnail questions", by acorn12

2020.02.13 22:23 "[Tiff] Tiff Thumbnail questions", by acorn12

As I want to work with some rather large, high-resolution TIFF files obtained from an older (HP?) scanner, I am looking for a way to allow my app to generate a usable thumbnail.

I have looked at the thumbnail utility I found as part of gnuwin32, presumably associated with libtiff, but it seems that, while it does create a thumbnail image, and apparently attaches it to the existing file - my assumption from the description and the resulting file size - tiffinfo & tiffdump don't seem to give me any information about two images - or I just don't know how to interpret the data

/c:\gnuwin32\bin\tiffdump.exe xxxxtLetter14Jan2001-page4-2400dpi-thumb.tif//
//Magic: 0x4949 <little-endian> Version: 0x2a//
//Directory 0: offset 59744 (0xe960) next 0 (0)//
//SubFileType (254) LONG (4) 1<1>//
//ImageWidth (256) SHORT (3) 1<216>//
//ImageLength (257) SHORT (3) 1<274>//
//BitsPerSample (258) SHORT (3) 1<8>//
//Compression (259) SHORT (3) 1<32773>//
//Photometric (262) SHORT (3) 1<0>//
//StripOffsets (273) LONG (4) 1<8>//
//Orientation (274) SHORT (3) 1<1>//
//SamplesPerPixel (277) SHORT (3) 1<1>//
//StripByteCounts (279) LONG (4) 1<59735>//
//PlanarConfig (284) SHORT (3) 1<1>//
//SubIFD (330) LONG (4) 1<71663894>//
//TIFF Directory at offset 0xe960 (59744)//
//  Subfile Type: reduced-resolution image (1 = 0x1)//
//  Image Width: 216 Image Length: 274//
//  Bits/Sample: 8//
//  Compression Scheme: PackBits//
//  Photometric Interpretation: min-is-white//
//  Orientation: row 0 top, col 0 lhs//
//  Samples/Pixel: 1//
//  Planar Configuration: single image plane//
//  SubIFD Offsets: 71663894//

FWIW, I am very new to TIFF & libtiff and, aside from trying to find a way to come up with a thumbnail image, am also very curious to find ways and utilities to help me understand the format better.

The questions I have not found answers to - after googling for the best part of a couple of days:

Results from one utility which looks very helpful, but because I don't know TIFF well enough, find a bit confusing are shown below:

 From the utility DPF mamager - using the Baseline TIFF 6.0



        Size: 68 Mb

Baseline TIFF 6.0

        Errors Warnings
Baseline TIFF 6.0 2 2

        File structure


  * IFD0 - Thumbnail
      o SubIFD - Main image

        Conformance checker

Show infos

          Baseline TIFF 6.0

Type    ID      Location        Description

        IFDI-0004       IFD1    Image IFD must have tag X Resolution

        IFDI-0005       IFD1    Image IFD must have tag Y Resolution

        TAG-284-0005    IFD1    PlanarConfiguration is irrelevant if  SamplesPerPixel is 1, and need not be included.

        TAG-284-0005    IFD1    PlanarConfiguration is irrelevant if  SamplesPerPixel is 1, and need not be included

More questions:

TIA for reading this far and for any pointers or other information to help me sort this out.