multiblend

• fix for a bug that might cause black banding on the bottom edge

• option to cache input images (--cache)
• fix for vignetting and corruption of right edge
• fixes to 16-bit processing (spotted by Matthias Kabel)
• nicer colouring for --save-seams

• fixes to GeoTIFF support
• fix for dark banding problems when compiling with g++>=4.7

About

multiblend is a multi-level image blender for the seamless blending of panoramic images, such as those created with PTAssembler (my personal favourite), Hugin, or PTGui. It is a significantly faster drop-in alternative to Enblend, although it lacks Enblend's advanced features.

Usage

Usage: multiblend [options] [-o OUTPUT] INPUT...

Options:
   -l X                  X > 0: limit number of blending levels to x
                         X < 0: reduce number of blending levels by -x
   -d DEPTH              override automatic output image depth (8 or 16)
  --nocrop               do not crop output
  --bgr                  swap RGB order
  --wideblend            calculate number of levels based on output image size,
                         rather than input image size
  --compression=X        output file compression. For TIFF output, X may be:
                         NONE (default), PACKBITS, or LZW
                         For JPEG output, X is JPEG quality (0-100, default 75)
  --cache                cache input images to disk to minimise memory usage
  --save-seams <file>    Save seams to PNG file for external editing
  --no-output            Don't perform blend (for use with --save-seams)
  --load-seams <file>    Load seams from PNG file
  --bigtiff              BigTIFF output (not well tested)
  --reverse              reverse image priority (last=highest)
  --quiet                suppress output (except warnings)

Pass a single image as input to blend around the left/right boundary.

Features

• Smart cropping

multiblend can intelligently open compressed uncropped TIFF files (such as those generated by older versions of PTAssembler) which itself can save a significant amount of time when dealing with large panoramas.

• Consistent and integrated seaming

Enblend blends input images one at a time, calculating and optimising a new seam line for each new input image against the intermediate output image so far. Not only is this slow (due to the repeated seaming and Enblend's use of an exact but complex algorithm for seam generation), it also makes the routes of Enblend's seams (and the degree to which images are blended) dependent on the order that input files are provided to it.

In contrast, multiblend calculates a unique composite seam for all images simultaneously, using a simpler algorithm:

(…and 716 other possibilities)
Enblend	multiblend

multiblend, however, doesn't optimise seams as Enblend does, and (probably) uses more memory while generating seams than Enblend does.
• Speed

Enblend similarly expends a lot of CPU cycles generating a full intermediate image for each new input image, with each intermediate image taking longer to generate than the last as the output image grows. This is where multiblend really wins out, as all images are (effectively) simultaneously blended:

Enblend	multiblend

The best result acheived in testing so far is a 172x speed improvement over Enblend for a 276mp image generated from a 7x7 array of 8mp input images (although Enblend ran out of memory before finishing, and only the 64-bit version of multiblend could complete the blend, so the true figure would have been higher).
• Smoother blending

The following false colour images show how multiblend can blend images more smoothly than Enblend (this particular example used multiblend's --wideblend option):

Enblend	multiblend

Other differences in implementation mean that multiblend is able to blend images which have very little overlap - or even none at all:

• 64-bit version

The download includes a 64-bit executable, which allows multiblend to use a greater amount of memory on computers running 64-bit versions of Windows.

• GUI

multiblend is also compatible (as long as no Enblend-specific options are set) with EnblendGUI.

Caveats

• multiblend is currently only available for Windows
• multiblend doesn't optimise seams, as Enblend does by default.
• multiblend uses a large amount of memory, and only has minimal caching features compared to Enblend, but the 64-bit version of multiblend does appear to be capable of blending larger panoramas than vanilla builds of Enblend.
• multiblend can not (yet) blend around image boundaries (Enblend's -w option).
• multiblend v0.3beta implements an approximation to image boundary blending
• multiblend requires an SSE-capable CPU. There is no non-SSE version available.

Acknowledgements

Contact the author