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
//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:
- The libtiff version I am using in my app is 4.0.1 - the gnuwin32 utilities are all version 3.8.2 - is there any significant difference in this respect
- why do these two utilities not show that there are in fact two images in the test file?
- is there a recommended utility to list all pages - or is there a recommended test image which I could refer to?
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
Baseline TIFF 6.0 2 2
* IFD0 - Thumbnail
o SubIFD - Main image
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
- the file structure shown is the inverse of what I would have expected
- it does show to images - why don't the Tiff utilities not show the same
- DPF manager output refers to 2 error and 2 warning - but the Tiff utilities don't.
- Is this due to the different versions? wrong options for the Tiff utilities? or ??
- is there a similar Tiff utility which would show the file structure? DPF Manager seems a bit overkill just to inspect that issue.
TIA for reading this far and for any pointers or other information to help me sort this out.