File:Kcc rescale 01 im point.jpg
Kcc_rescale_01_im_point.jpg (557 × 425 pixels, file size: 103 KB, MIME type: image/jpeg)
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Summary
DescriptionKcc rescale 01 im point.jpg |
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 "point" option -- i.e. merely retaining every other pixel (decimation). The result is very similar to the GIMP "no interpolation" option: interaction between spatially repeated structures in the engraving and the finite resolution has resulted in a highly visible Moiré banding pattern becoming apparent in the sky, the clouds and the building on the right, the result of spatial aliasing. Compared to the GIMP result, the phase of the Moiré fringes appears to be shifted by 180 degrees -- presumably because IM chooses to retain a different point of the four possible candidates. 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) |
Other versions |
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Source code
convert kcc.jpg -filter point -resize 50% kcc_im_point.jpg
Licensing
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:
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. |
Items portrayed in this file
depicts
1801
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 19:09, 6 March 2012 | 557 × 425 (103 KB) | Jheald |
File usage
Metadata
This file contains additional information, probably added from the digital camera or scanner used to create or digitize it.
If the file has been modified from its original state, some details may not fully reflect the modified file.
Orientation | Normal |
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Horizontal resolution | 400 dpi |
Vertical resolution | 400 dpi |
Software used | GIMP 2.6.12 |
File change date and time | 18:25, 5 March 2012 |
Color space | Uncalibrated |
Image width | 1,114 px |
Image height | 850 px |
Date and time of digitizing | 11:39, 4 June 2008 |
Date metadata was last modified | 11:39, 4 June 2008 |