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Sementara beberapa gambar yang diunggah ke Commons dalam kondisi sangat baik, banyak yang punya masalah. Meskipun kami tidak dapat memperbaiki beberapa masalah, seperti sudut yang buruk atau foto di luar fokus, banyak yang bisa diperbaiki setelah fakta dengan pengeditan digital. Halaman ini menjelaskan hanya beberapa dari masalah yang paling sering ditemui, bagaimana cara memperbaikinya, dan contohnya.
Gambar yang perlu dibersihkan tercantum di Category:Images for cleanup dan dalam banyak subkategori. Jika Anda menemukan gambar yang perlu perbaikan, dan tidak sesuai dengan salah satu skenario yang lebih spesifik di bawah ini yang memiliki tag sendiri, Menambahkan {{explanation}} ke halaman deskripsinya untuk menandainya untuk pembersihan.
Images with removable content
Unnecessary borders
Some images include borders that are not necessary and may be removed. Examples include:
- borders containing captions or other textual information better moved to the file description page, where it can be translated. (However, this is not always appropriate: In some forms of printed artworks, the text forms an inherent part of the look and feel of that type of artwork.)
- excess "padding" on the sides of an image, especially from scans of images from printed works. However, note that in some cases, where an image isn't quite rectangular, but nearly so, leaving a thicker border can give a better visual appearance, as cropping closer often emphasises this irregularity, by putting it near the perfectly-rectangular borders of the crop.
- a border which is not part of the image, or otherwise detracts from usage of the image under normal circumstances. In cases where the version with the border is meaningful or useful (see: Category:Images with intentional borders), a version without the border may be uploaded as a separate file.
Examples do not include:
- Removing a border that is part of the original artistic intent. For example, cropping an engraving to remove the hand-drawn edges of it will make it impossible to print that image in any way that resembles the look of the original printing. As a general rule, for historical artworks, if the border has been there from when it was created, we probably shouldn't remove it. This guideline was created to deal with people adding borders to their photos, not to encourage historical works to be changed away from their historical forms.
- As mentioned above, in cases where the edge of an artwork isn't quite rectangular, a thicker border can give a better visual appearance.
- Images where removing the border gives a false impression. For instance, photogravures are usually slightly darker than the surrounding paper, and this makes photogravures instantly recognisable. If the paper is cropped out, they instead look like the uploader did not do a proper white balance adjustment. Similarly, File:Alfons Mucha - 1896 - La Dame aux Camélias - Sarah Bernhardt.jpg is a yellow-tinted image printed on white paper, not an image printed on yellowed paper, but cropping out the border would make the latter seem like the truth.
- A featured picture on Commons or any Wikipedia (as a rule of thumb). It's generally a bad idea to make large changes to an image after its promotion to featured picture, and the border could have been cropped during the featured picture nomination process, had it been desired.
In cases such as these, the border is necessary, at least in the main image. It is, of course, always acceptable to use {{Extract image}} to request a copy of the image to be uploaded without the border, if that is better for a specific use, but such extracted images generally should not be the default image.
If you see an image with unnecessary borders, add the template {{Remove border}} to it to request a cropping, which adds it to Category:Images with borders. If you see an image with a meaningful border but would like to request a version without the border, add the template {{Extract image}} to it to request an extraction, which adds it to Category:Images requiring extraction.
How to process a crop request: Trim the image to the relevant area only. If cropping a JPEG, consider using a lossless cropping tool such as jpegtran. You can also use Cropbot or CropTool. If the cropped area contained text, be sure to include it in the image description.
How to process an extraction request: Upload the cropped image to a new name.
Non-free frames
Similarly, some images include nonessential decorative elements such as 3D frames that are legally problematic and need to be removed. In particular, {{PD-Art}} images may not contain 3D frames. If you see an image like this, add {{Non-free frame}} to it, which adds it to Category:Images with non-free frames.
What to do: If the frame is rectangular, crop the image to the area of the free image only. If cropping a JPEG, consider using a lossless cropping tool such as jpegtran. You can also use Cropbot. If the cropped area contained text, be sure to include it in the image description. If the frame is round, oval, or some other odd shape, use an image editing tool to select the area containing the free image, then invert it and blank the rest to white or (for PNGs/TIFFs) transparent. If you are an admin, you may wish to delete the old revision containing the border.
Text in a specific language and/or script
Some images contain descriptions or captions in a specific script or language. In some cases, this text will be an inherent part of a historical artwork, and should be left alone. With that exception, though, as far as possible, any descriptive text (captions, annotations, legends) should be within the file description page, not in the image itself.
What to do: redesign the picture to describe the elements with color codes and/or numbers, in order to achieve a language neutral form. This would allow its use in all Wikimedia projects and, more importantly, all Wikimedia languages. If you see an image like this, add {{Convert to international}} to it, which adds it to Category:Images requiring internationalisation.
Note that language specific files are acceptable, especially for complex diagrams, if there is a language-neutral version as well. Such files should be linked to each other. It is also less important for SVG files to have a language-neutral version, as it is easy to edit these to modify the language.
Images with better file format options
JPEG images that should be PNG or SVG
Certain images (practically anything but photos) look and work better (and may require less room) in either a lossless format or a vector graphics format, for which we use PNG and SVG files respectively. These generally include flags, graphics, icons, diagrams and certain screenshots (such as from old video or arcade games, but not newer ones with high color depth). If you see an image like this, add {{BadJPEG}} to it, which adds it to Category:Images with inappropriate JPEG compression. Also consider {{Convert to SVG}} if applicable. (If the JPEG compression of an image is too “high”, tag files with {{Overcompressed JPEG}} instead.)
What to do: Remake the image or retouch it (making it sharp) using image editing software, as described at w:Wikipedia:How to reduce colors for saving a JPEG as PNG. You should not convert JPEG files directly into PNG files without modification, since this won't improve quality and will just make a larger file. See below for some advice on SVG. Note that a new file will have another name. Once done, mark the old image with a {{Superseded}} tag.
Example: Before, After (see more in category: Posterized to reduce file size)
Warning: Unfortunately, due to the software limitations, PNGs are a bit poorly handled, not being displayed at large sizes, and not having extra sharpening applied when thumbnails are created, leading to slightly blurry thumbnails (see phab:T20014 and example). As such, it's often best to offer both a JPEG and PNG version of any image where having a lossless copy is useful.
- Note: Currently the Wikimedia-software does only sharpen thumbnails of true- and high-color PNGs, so color-indexed images are unsharper (see phab:T31659 and example).
PNG or JPEG images that should be SVG
Images composed of simple shapes, lines, and letters are often better expressed using vector graphics. These have a number of advantages such as making it easier for subsequent editors to edit them, enabling arbitrary scaling at high quality, and sharp high-resolution renderings for print versions. If you see an image like this, add {{Convert to SVG}} to it, which adds it to Category:Images that should use vector graphics. Certain JPEGs and PNGs are not suitable for transfer to the SVG format. These include heavily or artistically shaded images, or non-free images on other projects such as those of logos (conversion to a scalable format can represent a copyright violation). Images that have been uploaded at a high resolution and good quality are a lower priority for transfer to the SVG format. Efforts are better focused on converting lower quality, smaller images that will be substantially improved if redrawn as a SVG. Images which will appear the same but will require marginally less file space are a lower priority.
Raster images generated by libre (free) software programs, for which a source file is made available under a libre license, is also of lower priority. In fact, such images if the source file is provided should be left alone probably if the program does not provide SVG output, or else it may even be *harder* for subsequent editors to modify the image (the opposite of the stated goal above). It does help to request a feature for SVG output from the developers of such programs.
What to do: using vector graphics production software (see en:Comparison of vector graphics editors), remake the image. The original image can often be used as a template. Some notes:
- A very simple image with known dimensions and colors, like a plain flag, may be easier to make from scratch.
- A raster image can be vectorized, but be careful: it will almost certainly differ from the original and need some manual work. Do not leave the raster image in the SVG when saving it for upload. Check for redundant code which does not affect rendering (but don’t forget about scalability).
- Sometimes people base their images on a raster “thumbnail” from a WMF project. See the next item.
- Raster images based on the vector or raster maps from Commons should often be not just vectorized, but remade based on those maps (see Blank maps, SVG maps, Maps).
- Graphing tools like gnuplot and R produce high quality SVG output plots in a repeatable way. It is helpful if the source code of the gnuplot commands used to create the graph are included in the description page of the image so that other users can regenerate the plot when necessary.
- For chemical structures, this page has relevant information.
If the image is derived from a third-party source, first check whether a vector version is available from that source. It is easier to convert a PDF into SVG than to remake the entire file.
2D files better represented in 3D
Commons now supports uploads of STL files. Previously, contributors wishing to show a three-dimensional image would resort to uploading a video of the object rotating, or a still image of different views of the object. These are acceptable as ancillary files, but there are cases where the original 3D shape is the best way to convey the desired information. Therefore, there is a template listing files to have a source or derived 3D version uploaded: {{Convert to STL}}.
Thumbnail issues
PNG photos that require a JPEG version
Although PNG is not a bad way of losslessly storing photographs, any thumbnail of a PNG appearing in an article will be in PNG format. The result is that these thumbnails have a large filesize, making them slow to download for many users (typically, about 10 times larger than JPEG thumbnails). Although ideally the software would be able to create JPEG thumbnails of PNG images, right now it can't. Additionally, sharpening is applied to JPEG thumbnails but not to PNG thumbnails, and sharpening is usually desirable for photographic thumbnails. See phab:T192744 for details on the design decision to not sharpen PNG thumbnails.
What to do: Create a JPEG version of the file and upload it; quality is not important when we do it this way as long as it looks good. Place {{PNG with JPEG version}} on the original PNG's page and {{JPEG version of PNG}} on the JPEG's page. This alerts people to refer to the JPEG version in articles, but to make edits to both versions, based on the PNG version.
Example: PNG before, PNG After, JPEG after
Large PNG, TIFF and GIF files
Above a certain size, PNG, TIFF and GIF files are currently not provided with thumbnails by Commons' MediaWiki software (an error message is displayed). JPEG versions linked to the original file via {{Compressed version}} (although it does not need to be a compressed version) should be uploaded for preview purposes and used in Wikimedia websites. See COM:MAXTHUMB.
Quality issues
Images scaled down from their original resolution
Partly because MediaWiki image pages scale down images by default, it's a common mistake to upload a scaled-down, lower-resolution image to Commons than the original image. This is unnecessary and undesirable; large images are necessary for use in print and other situations. If you see an image like this, add {{Thumbnail}} to it, which adds it to Category:Images uploaded at reduced resolution.
What to do: Upload or locate a larger resolution image of the same filetype. If the image is otherwise identical, tag it with {{duplicate|Image:example.jpg}} and give for the parameter the larger image. You or the person deleting it should use "check usage" to ensure that the small image is no longer used. See COM:Dupe for more information. If the larger image has differences, tag the old version with a {{Superseded}} tag instead.
EXCEPTION: For exceedingly large images, such as this 690 megapixel image, Commons' file viewers such as {{LargeImage}} can break, and the maximum thumbnail size Wikipedia will create is still far, far below the size of the image itself. In these cases, uploading a courtesy copy that can be viewed with the file viewers may be appropriate.
Example 1 (identical): Smaller version, larger version
Example 2 (differences): Smaller version, larger version
Wikimedia projects other than Commons, particularly those accepting non-free content, may prefer uploading of thumbnails for some purposes.
Sideways pictures or pictures with noticeable camera tilt
These images need to be rotated so they're upright.
For slightly tilted images this may involve cropping and/or cloning to remove or fill in new areas.
If you see an image like this, add {{Rotate}} to it, which adds it to Category:Images requiring rotation.
If you want to rotate images by 90, 180, or 270 degrees add the parameter |degree=90/180/270 to let it rotate automatically by Rotatebot (e.g. {{Rotate|degree=90}} or simply {{Rotate|90}} to rotate 90° clockwise).
Such rotation is done with the best available method to keep loss of image quality to a minimum (it is called "lossless", though this is usually not quite true) [1] .
Images containing regular noise, texture, or interference
A variety of sources can introduce unwanted overlaid patterns into an image, such as halftone patterns and text from the opposite page side bleeding through in scanned images and the presence of electromagnetic interference during image creation or processing. All of these (and also naturally occurring patterns, which should not be removed, such as fences and parts of other man-made objects) can cause moiré patterns to occur when resampling images without extra care taken to avoid them – something that is prone to happen in automatically generated image thumbnails for articles in particular.
What to do: Add {{CleanFFT}} to the image to include it in Category:Images containing regular noise. After that, ideally, find a better version of the picture that does not contain the noise. If this is not possible, in many cases you can clean up this type by editing the image in the frequency domain by doing either a Fourier or wavelet transform on the image. Such transformations can be done in both GIMP and Adobe Photoshop with the aid of suitable plugins. For more information on how to do this, see Commons:Cleaning up interference with Fourier analysis. If the size of the patterned noise is significantly smaller than the image details' then simply slightly blurring the image or using other general denoising methods can be very effective in eliminating them without any degradation to image quality, too.
Examples:
Low quality images
Some images are not sufficient to clearly demonstrate the subject of the image; whether by being too blurry to digitally fix, being of small resolution and/or compression, not properly demonstrating the subject of the image, or being visually unappealing in another way. New versions with higher quality should be found and used instead. Low-quality images can be tagged with {{Low quality}} (or if applicable {{Blurry}}) to add them to Category:Images of low quality.
What to do: get a camera and take a better image, or try to find one under a free license. See, for example, Commons:Free media resources.
Versioning
For cleaned up media, a rule of thumb is to:
- first upload the original, dirty media;
- upload the cleaned up version over the dirty version.
This allows the dirty version to be recovered if desired, but not included or linked to directly.
Alternatively, one can upload the cleaned up version under a different name; this is particularly useful if several different clean-ups are done. See discussion on cropping.
Technical notes
- ↑ It is called a "lossless" method because it does not involve recompressing the entire image using the JPEG lossy compression algorithm, which involves a loss of image detail (though the JPEG algorithm attempts to lose image detail the human eye does not notice much, recompressing an image that has already been compressed with a good compromise between file size and image quality may noticeably worsen image quality). Although Rotatebot uses jpegtran to losslessly rotate JPEG images, the rotation is not completely lossless as images of sizes which are not a multiple of the JPEG block size (16×16 pixels for color images, 8×8 pixels for grayscale images) have to be cropped to a block boundary. For images of a reasonably large size this cropping is usually not noticeable. Truly lossless rotation can be done by changing only the EXIF Orientation tag (e.g. using the exiftran or Geeqie programs), as this implements rotation for display purposes only (assuming the image viewing software respects the Orientation tag), without modifying the original image.
See also
- Category:Videos for cleanup
- Commons:Graphic Lab – the place to request image improvements
- Commons:Templates#Digital editing required
- Category:Image cleanup templates
- English
- w:Wikipedia:Graphics tutorials
- w:Wikipedia:How to improve image quality
- w:Wikipedia:Preparing images for upload
- w:Wikipedia:Image use policy
- w:Wikipedia:Picture tutorial
- w:Wikipedia:Graphic Lab (cleanup is its job)
- German
- w:de:Wikipedia:Fotowerkstatt (cleanup images is its job)
- w:de:Wikipedia:Grafikwerkstatt (cleanup graphics is its job)