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File:Kcc rescale 04 im triangle.jpg

Kcc_rescale_04_im_triangle.jpg ‎(557 × 425 pixels, file size: 70 KB, MIME type: image/jpeg)

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English: Part of a series of images to compare and contrast the levels of spatial aliasing that can result when an image that contains some strong spatial frequencies is digitally rescaled. An image of an 1801 engraving of King's College Chapel, Cambridge was used as a test object, and resized to 50% using different filters and different programs.

The image on this page was resized to 50% using Image Magick 6.7.5 with the "triangle" option -- i.e. taking into account nearby pixels using a ramp filter.

Compared to the box filter, this time the Moiré banding seems to be completely suppressed; but at the same time the buttresses of the chapel are also noticeably less sharp, making the building softer than it was with the box filter.

Other images in the series look at the results of using various available lowpass filters to try to minimse or suppress such artefacts.
Date
Source This file was derived from: F. Roffe after P. Nash (1801) - King's College Chapel - sanders13001.jpg
an engraving first published in 1801.
Author John Roffe (1769-1850), engraver, after Frederick Nash (1782–1856)
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Source code edit 

convert kcc.jpg -filter triangle -resize 50% kcc_im_triangle.jpg

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This is a faithful photographic reproduction of a two-dimensional, public domain work of art. The work of art itself is in the public domain for the following reason:
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The official position taken by the Wikimedia Foundation is that "faithful reproductions of two-dimensional public domain works of art are public domain".
This photographic reproduction is therefore also considered to be in the public domain in the United States. In other jurisdictions, re-use of this content may be restricted; see Reuse of PD-Art photographs for details.

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current19:08, 6 March 2012Thumbnail for version as of 19:08, 6 March 2012557 × 425 (70 KB)Jheald (talk | contribs)

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