[a07dce]: TODO Maximize Restore History

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This file documents the activities required before we release version
3.0.0 of the library.

* Very little testing has been done in 16 bit images.


* Perhaps the most pressing issue is to create a good set of tests for
  each of the tools. So far we only have tests for PTmender (and only 2).

What we need:

* PTmender. We need to test each of the projections, and each of the
  different types of input projections.

* All others: they desperately need a test.

Issues with creating the tests:

* tiffcmp is good for comparing just the data in tiffs. But once one
  starts using the non-deterministic parts of panotools (such as
  colour correction and feathering) it is impossible to use them. What
  we need is some type of program that reads the data inside an image
  and compares it to be "similar" within certain threshold.

* we also need the equivalent of tiffcmp for PSDs, where we can
  specify we want to compare the data, not the metadata. The small
  parser I have written might be exactly what we need: ignore all
  metadata. It might be necessary to compare the "layer and masks
  block", but not the ColorModedDataBlock or the Metadata block. It
  might not be as easy as it sounds, because offset might have
  shifted. 

======================================================================
KNOWN BUGS:

----------------------------------------------------------------------
All tools:

- Command line processing. All tools should have similar command line
  processing. This needs to be checked, and updated, if
  necessary. 

  * I have updated most of them to be consistent, but I might have
    missed something. Needs to be checked.

- PTcrop tries to read the entire image at once. With a huge image I
   got a segfault from inside libtiff. It needs to be rewritten to read
   only one line at a time (not critical for 3.0.0, but it would be nice).

- PTroller runs _extremely_ slow. I need to find out why. (not
  critical for 3.0.0)

- PTtiff2psd. I fixed a major bug in the implementation of writing the
  metadata. I suspect that there are still some "issues" regarding
  this. I have also written a small top-down parser to verify the data
  written. 

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panoinfo:

----------------------------------------------------------------------

PTmender:

DESIRABLE:

- PTmender is not properly calculating ROI for some images. In
  particular (at least) circular fisheyes that cover the zenit or the
  nadir. Currently these types of images require full size processing
  (as opposed to cropped processing).

----------------------------------------------------------------------
PTtiff2psd:
 
DESIRABLE:

Create PSDs of one layer 8 and 16 bit images

======================================================================

After 3.0.0:

DESIRABLE FEATURES:
 
 - Output a text file with the names of the files processed and extra
   information, such as size

 - If somebody wants full compatibility with PTstitcher, a new program
   can be added that does all the work. It will be a "superset" of many
   of the current pano tools.
 
----------------------------------------------------------------------
PTblender:

DESIRABLE:
 
 - Feature: Create photoshop curves and maps for HSV colour
   corrections. Probably not for 3.0.0
 
----------------------------------------------------------------------
PTroller:
 
DESIRABLE:

- PTroller: Add the ability to stack and add composing
  images (PTtiff2psd is able to do stacking and compositing)
 
----------------------------------------------------------------------
 PTuncrop:

----------------------------------------------------------------------
 PTcrop:
 
DESIRABLE

- It needs to be able to crop images as a "set" (that is, compute the
   bounding rectangle of a group of images) not only as a single one.

- Compute the inner rectangle with the largest area (not a priority)


----------------------------------------------------------------------
 
PTtiff2psd:
 
DESIRABLE:

Create PSDs of one layer 8 and 16 bit images

 ----------------------------------------------------------------------
PToptimizer:

* Ready for 3.0.0
 
----------------------------------------------------------------------

 
----------------------------------------------------------------------
 LONGER TERM:
 
 * Allow tools to read their parameters from the PTstitcher script.
 
 * Add support to all the tools for 16 bit, and 32 bit images (it is
   kind of mixed at this point)

----------------------------------------------------------------------
PTblender:

- Pre-compute which images could actually overlap from their TIFF
  offsets, adding only these to a linked list of pairs.  Might as well
  support cropped TIFFs where possible.  This will really help people
  who do >20 image multi-row sphericals (since the current algorithm
  loops over all pixels in the image N^2 times).  For such panos, it
  may even be worth calling PTcrop (when it exists) first on the
  uncropped images.

- Replace the two inner nested loops in ReadHistogram with one loop
  over the linked list of "possible match" images, and invert the
  order of the loops:

    for (each row) {
            read_row_from_images(row,&row_buffer); // careful with crop
            for (each match in matching_images_list) {
                    if (row intersects both image boundaries) {
                            for (each pix in row) {
                                    if pixel_include(row,pix,im1,im2,trim)
                                            add_to_histogram(pix,match);
                            }
                    }
            }
    }   

- Factor out the code which decides whether to use a given pixel in
  the histogram into a separate function (pixel_include() above), and
  pass it an options structure which gives it what it needs to know
  (the optional trim factors, etc., called 'trim' above).  This is
  also where separate mask data could be used, but the "graymask"
  method currently employed may obviate that.

- Simplify the actual histogram remapping and subsequent color
  correction code:

  1. Always match all three histograms, RGB.  Impose "brightness only"
     or other constraints on the mapping functions at the very end
     (see below).  No HSV computations are ever performed.

  2. Use a single routine to compute a mapping function (table) from
     histogram 1 (source) to histogram 2 (target).  This routine will
     simply:

	a. Form cumulative totals of the both histograms.
        b. Create the 256 element floating point mapping function z
           which maps between them (one for each of RGB).

     This function will be called many times, so needs to be short and
     sweet.

  3. Build a ragged array of length n_images, with each element
     holding a linked list of all other images to which it matches,
     keeping track of pixel overlap count, and omitting matches
     without enough pixels in overlap.

  3. Compute the floating point mapping functions z for all pairs in
     the ragged array..  There is one z per pair for each of RBG.

  4. "Anneal" the (potentially long list of) mapping functions z over
     the entire image:

	a. For each image, compute a master mapping function m for the
	   image, from the overlapping pixel count-weighted average of
	   all the modified sub-functions to all neighbors.

        b. The modified sub-function z' to a neighbor will depend on
           i) the mapping function between the two, z, and ii) the
           master function m of the neighbor, as:

		z'=m^-1 z 

	   The inverse of a mapping function m is that function which,
	   when m is run through it, produces the unit vector
	   (0..255).  In the first round, all master functions are set
	   to the unit vector (0..255), and z'=z.

	c. Repeatedly iterate over all images in this way until all
	   master mapping functions converge.  Convergence can
	   progress non-uniformly (image by image); each image is
	   marked as converged once its master function converges.
        
     Note that a reference image is no longer needed... the average
     best mapping to make all images compatible is automatically
     developed (e.g. for a range of brightnesses, the "average"
     brightness will be targeted).  If a reference image is desired,
     it is marked "converged" before the first round of annealing, and
     everything proceeds in the same manner.

  5. Normalize each image's annealed master mapping function, subject
     to the (optional) user constraints:

	-t 1 (brightness only): m(r) = m(g) = m(b) (one average table).
        -t 2 (color only):      m(r) + m(g) + m(b) = I (unit vector)

  6. Convert all normalized, annealed master mapping tables to byte,
     by rounding, perhaps with some care taken to avoid banding caused
     by large gaps.

  7. Run each image's data through its master mapping table and write
     out to output image.

- No flattening (separate tool).

- Add an optional debug switch to enable all that Debug.txt output
  (just to stdout).
----------------------------------------------------------------------

GetROI

   Hello
   I used ptmender to play with the projections. I use the SVN-source from 
   SF. I converted a equirectangular panorama to lambertazimuthal projection.
   I had the problem that the resulting image-file often displays not the 
   whole projection. The reason for this problem seems to be the x_jump in 
   the getROI-function:
   
   Depending on the image size and because of the x_jumping getROI 
   calculates sometimes wrong left/right values.
   
   I could solve my problems by changing the line 504 in PTcommon.c from
       x_jump = (y==0 || y==TrPtr->src->height) ? 1 : TrPtr->src->width/2;
   into
       x_jump = (y==0 || y==TrPtr->src->height ||
           abs(y - TrPtr->src->height/2)<=5) ? 1 : TrPtr->src->width/2;