In an attempt to identify the best tools available, this review compares images enlarged using several digital image interpolation (resizing / resampling) methods including S-Spline, Genuine Fractals, Lanczos, Bicubic, Stair Interpolation, Kneson (standard), QImage (Vector, Pyramidal), pxl SmartScale, PhotoZoom Pro 2, Pictura, Resize IT, Blow Up.

 

Photo interpolation is the process by which the number of pixels comprising an image is increased to allow printing enlargements that are of higher quality than photos that are not interpolated.  Interpolation is commonly needed to make quality large prints from digital photos and film-scanned images.

 

Most recent interpolation samples added March 14, 2007 (SizeFixerXL by FixerLabs).

 

Regarding Genuine Fractals update from 3.0 to 3.5...  test results using the 8 bit test images below showed no noticeable differences in Genuine Fractals 3.5 from 3.0.  The benefit of 3.5 over 3.0 is support for 16 bit images.

 

Genuine Fractals 4.1 is out.  The interpolation algorithm remained the same from 3.5 to 4.0 (not sure about 4.1 yet).  The difference between 3.5 and 4.0 was improvements in workflow (e.g. can be used within photoshop instead of first saving to a file from what I understand).  This software as well as pxl smartscale are now part of

 

 

 

Interpolation tools included in this comparison:

 

Bicubic Interpolation:  a standard interpolation method included in many photo editing tools including Photoshop, PaintShop Pro and others.

Stair Interpolation - photoshop action (by ):  uses bicubic interpolation in small increments which is thought to produce better results than bicubic (and perhaps other methods)

Lanczos Interpolation:  interpolation method thought to be of quality.  Available for free as part of .

Kneson (standard):  featured method of interpolation.

QImage (Vector):  A photo printing application that includes interpolation of output (by ).

Genuine Fractals 3.0:  latest version of the interpolation software (noticeable differences from v2).  5/17/2004 Note:  3.5 has just been released.

pxl SmartScale:   Photoshop plug-in from .

Sar Image Processor:  - interpolation tool by Steven A. Ruzinski, Ph. D.

Qimage (Pyramidal):  newest addition to the photo printing package

Resize IT:  Interpolation plug-in for Photoshop by Brian Spangler at

Pictura:  interpolation and image correction (noise, sharpening) application now in alpha stage of development. 

Photozoom Pro 2:  interpolation software from  .  PhotoZoom Pro 2 is the latest evolution of the S-Spline Pro product (formerly from Shorcut).

 

Per the Celartem website (July 2005):  pxl SmartScale from Extensis and the Genuine Fractals product from LizardTech were sold to

 

Genuine Fractals 4.1:  is available from .

 

Zoom Engine from

 

Blow Up from

 

SizeFixerXL from

 

Interpolation Testing Method

 

The photos were taken with a 5mp digital camera.  One thing to watch for is the amount of noise present in the resulting images.

 

Note:  the samples are posted here so you can see the results for yourself.  Different people will identify subtleties between methods that suit their personal taste.  People are all over the board with respect to which one they like the best.  As a result, my personal opinion is not included here.  Another reason I do not advocate a specific interpolation tool is so that new tool makers will allow me to post samples with their tool.  I believe this approach will result in more information being made available to those who might be interested.

 

New tools are added periodically.  Feel free to suggest additional tools as they become available.

 

If you own a tool that is not included here and you would like to compare, send me a and I can send you the test file along with instructions.  If you are a tool maker, please be prepared to make your application available to me for testing.

 

See an alternative comparison of tools here:

http://www.general-cathexis.com/interpolation/index.html

 

The different methods compared

 

Test photo 1 of 3:  1407 x 612 pixels interpolated to 9000x3915.

resampling test image

 

This sample was enlarged without using any interpolation.

no resampling example

 

,

 

Note:  sharpening using Photoshop Unsharp Mask was applied after interpolation to the crocodile photo examples.

 

Kneson Standard, QImage (Vector), Genuine Fractals 3.0, pxl SmartScale, SAR Image Processor, Photozoom Pro, QImage (Pyramidal), ResizeIT and Pictura results are further down the page.  .

 

Click the thumbnails below to open separate windows with full size pictures.

Bicubic Lanczos PhotoZoom Pro 2 Stair Interpolation Genuine Fractals 3.0 bicubic interpolation sample lanczos interpolation sample stair interpolation sample

 

Test Photo 2 of 3:  2558x1809 interpolated to 8000x5658

No sharpening or other post processing has been performed on these samples this photo.  Note:  you might want to save copies of the test pictures and sharpen them.  Noise level differences stand out after sharpening.  Particularly in the Duck Eye sample.

 

Kneson Standard, QImage (Vector), Genuine Fractals 3.0, pxl SmartScale, SAR Image Processor, Photozoom Pro, QImage (Pyramidal), ResizeIT and Pictura results are further down the page.  .

 

Click the thumbnails below to open separate windows with full size pictures.

 

Bicubic Lanczos PhotoZoom Pro 2 Stair Interpolation Genuine Fractals 3.0

 

Newer Additions

Click the thumbnails below to open separate windows with full size pictures.

(users will need to scroll horizontally to see all methods)

-->  scroll to see newer additions -->

 

 

pxl SmartScale - sample images used default settings:  Sharpness: Normal, Edge Contrast: High, Edge Detail: High, Extreme Edges: Off

S-Spine Pro - sample images used the Photo setting.

Sar Image Processor - this tool includes multiple interpolation options.  Interpolation of test photos was performed by the tool author using the method of his choosing.

Resize IT - samples use Spline 64 - increments set to 4

Pictura is a new application in the alpha stage of development.

Photozoom Pro 1.095 - Crocodile interpolated using the S-Spline interpolation method, Photo-Detailed setting, Still photo interpolated using the Graphics-Strong Edges setting (unsharp mask off)

Genuine Fractals 3.5 is now available.  Now supports 16 bit images.  Interpolation tests using these images didn't show any noticeable differences; but they're all 8 bit images so the results aren't posted.

Blow Up enlargements used setting of 100% sharpening and 50% added noise.

 

Test photo 3 of 3:  2560x1704 interpolated to 9000 x 5991

 

Photo was interpolated then sharpened (unsharp mask 300, 2, 0)

Dust and Scratches filter applied (8, 14)

Neat Image was used to remove noise

photo was sharpened again using the same settings as above

 

Note:  Newer tools may not appear here.  This test took a while so may not be performed for new additions.

 

Click the thumbnails below to open separate windows with full size pictures.

 

Stair Interpolation Bicubic Genuine Fractals 2.0 Kneson Progressive Kneson Standard Lanczos QImage Vector S-Spline 2 Genuine Fractals 3.0            

 

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