Wether a multi-page TIFF uses multiple IFDs or uses one IFD with multiple SubIFDs is implementation dependent. Though, I think most probably just use multiple IFDs. The basic structure of an IFD and a SubIFD is essentially the same. The main difference is where you find their offsets and the offset for the next IFD. If you want to just grab all of the regular IFDs, that is pretty easy to do. The "next offset" to the next IFD is at the end of the IFD's structure. You just go to that next offset and then process the IFD just like you did the first one. Grabbing SubIFDs requires you to look for the SubIFD tag (330 or 0x014a) inside an IFD and process the value field into a list of offsets values as a []uint32. There could be one or more offsets. Keep in mind that with SubIFDs, while the tag ID, its purpose, and format are documented and not intended to be changed, some manufacturers will ignore this and reuse the field for something else. Sony did this on at least one camera model that I know of. Most uses I have seen adhere to the original purpose though.
If you want to see some (unfortunately) undocumented and very incomplete code for processing the basic data structures of a tiff (i.e. getting IFDs and SubIFDs, but not going as far as processing the actual image data), I posted some code here github.com/google/tiff. The godoc page <https://godoc.org/github.com/google/tiff> is more useful I think. I started on this code a while back, but have not had time to revisit it in depth in a while. Andrew, which camera makes and models do you shoot with? I have a Nikon D200 and a D800. I started working on model specific data structures for multiple camera models at https://godoc.org/github.com/google/cameraraw. I actually have code to generate those go files based on a TIFF/DNG/RAW file. It is just not checked in anywhere. On Monday, September 25, 2017 at 7:10:40 AM UTC-4, Tad Vizbaras wrote: > > If you implement decoder I can provide sample multi-page TIFF files to see > if it is working. > > On Sunday, September 24, 2017 at 2:48:50 PM UTC-4, Andrew O'Neill wrote: >> >> A while ago I reading Adobe's doc's on SubIFD's since that is needed for >> decoding Nikon's RAW files. Is this a similar thing or is it just reading >> all the IFD's? I plan to implement a SubIFD decoder for tiff, unless >> someone else has done it. >> >> On Sun, Sep 24, 2017 at 8:21 PM Tad Vizbaras <eta...@gmail.com> wrote: >> >>> Sad. >>> >>> Any chance to add multi page support to this? I am in desperate need for >>> multi-page TIFF support. >>> >>> >>> On Sunday, September 24, 2017 at 9:20:31 AM UTC-4, Guy Allard wrote: >>>> >>>> This package does not appear to support multi-page TIFs. Decoder >>>> initialization only reads the 1st IFD. >>>> >>>> On Friday, September 22, 2017 at 1:49:47 PM UTC-4, Tad Vizbaras wrote: >>>>> >>>>> No problem reading single page TIFF images using: >>>>> "golang.org/x/image/tiff". >>>>> >>>>> It works great. >>>>> >>>>> >>>>> Question: how to read multi-page scanned TIFFs? How to access pages 2, 3, >>>>> etc.? >>>>> >>>>> >>>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "golang-nuts" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to golang-nuts...@googlegroups.com. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
