Commons:Média k opravě

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This page is a translated version of a page Commons:Media for cleanup and the translation is 25% complete. Changes to the translation template, respectively the source language can be submitted through Commons:Media for cleanup and have to be approved by a translation administrator.

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Zatímco některé obrázky nahrané na Commons jsou v dobrém stavu, mnoho z nich mají určitý problém. Zatímco nemůžeme některé problémy vyřešit, jako například špatný úhel nebo rozostřená fotografie, mnoho problémů lze vyřešit digitální úpravou. Tato stránka popisuje jen některé z nejčastějších problémů, jak je opravit, a jejich příklady.

Obrázky, které potřebují opravit, jsou v kategorii Obrázky k opravě a mnoha subkategoriích. Pokud najdete obrázek, který potřebuje zlepšit, a nespadá do jednoho ze specifičtějších případů níže, který má vlastní štítek, přidejte {{Cleanup image|vysvětlení}} do popisu souboru k označení pro opravu.

Viz také: Commons:Preparing images for upload

Obrázky s odstranitelným obsahem

Zbytečné okraje

Některé obrázky obsahují okraje, které nejsou potřebné a měly by být odstraněny. Příklady zahrnují:

  • okraje obsahující popisky nebo jiné textové informace, které se spíše hodí do popisku souboru, kde mohou být přeloženy. (Ale toto není vždy vhodné: V některých formách tištěných děl je text nedílnou součástí designu daného typu díla.)
  • přebytečné „okraje“ na krajích obrázku, především ze skenů obrázků tištěných děl. Nicméně mějte na paměti, že v některých případech, kdy obrázek není zcela obdélníkový, ale je blízko, ponechání většího okraje může být prospěšné pro lepší vzhled, kde ořez k užším okrajům může často tuto nedokonalost zvýraznit tím, že ji zobrazí blíže perfektně obdélníkovému okraji ořezu.
  • okraj, který není součástí obrázku, nebo jinak odrazuje od použití obrázku za normálních okolností. V případech, kdy je verze s okrajem užitečná a dává smysl (vizte: Kategorie:Obrázky s úmyslnými okraji), verze bez okraje může být nahrána jako nový soubor.

Příklady nezahrnují:

  • Odstranění okraje, který je součástí původního uměleckého záměru. Například ořez rytiny k odstranění ručně nakreslených okrajů způsobí nemožnost obrázek vytisknout jakýmkoliv způsobem, který bude připomínat původní vzhled obrázku. Platí obecná poučka, že v případě historických děl, pokud zde již okraj byl při vytvoření, patrně by neměl být odstraňován. Toto pravidlo bylo vytvořeno kvůli lidem přidávajícím okraje ke svým fotografiím, nikoliv k podnícení změn historických děl z jejich původní historické formy.
  • Jak bylo zmíněno výše, v případech, kdy okraj díla není úplně obdélníkový, širší okraj může zlepšit vzhled.
  • Obrázky, kde odstranění okraje může vyvolat nesprávný dojem. Například, fotogravury jsou běžně malinko tmavší oproti papíru, na kterém jsou natištěné, a toto je silným poznávacím znakem. Pokud by byl papír oříznut, fotografie najednou vypadá, jako by přispěvatel nesprávně upravil vyvážení bílé. Podobně File:Alfons Mucha - 1896 - La Dame aux Camélias - Sarah Bernhardt.jpg je žlutě zabarvený obrázek natištěný na bílém papíru, nikoliv obrázek natištěný na zažloutlém papíru, ale ořez okraje by vytvořil dojem druhého případu.
  • Obrázek týdne či měsíce na Commons nebo jakékoliv Wikipedii (obecná poučka). Obecně je špatný nápad činit velké změny v obrázku poté, co byl zobrazen na obrázku týdne či měsíce, a okraj mohl být oříznut během nominačního procesu, kdy by to bylo přínosné.

V těchto případech je okraj nezbytný, alespoň v hlavním obrázku. Samozřejmě je vždy možné použití šablony {{Extract image}} pro zažádání kopie obrázku k nahrání verze bez okraje, pokud je lepší pro specifické použití, ale takto extrahované obrázky by zpravidla neměly být hlavními výchozími obrázky.

Pokud vidíte obrázek se zbytečnými okraji, přidejte šablonu {{Remove border}} pro požadavek k ořezu, což obrázek přidá do Kategorie:Obrázky s okraji. Pokud vidíte obrázek s užitečným okrajem, ale rádi byste požádali o verzi bez okraje, přidejte šablonu {{Extract image}} pro požadavek k extrakci, což obrázek přidá do Kategorie:Obrázky vyžadující extrakci.

Jak zpracovat požadavek k ořezu: Obrázek ořízněte pouze k relevantní oblasti. Pokud ořezáváte JPEG obrázek, zvažte použití bezztrátového ořezového nástroje, jako je jpegtran. Můžete také použít Cropbota nebo CropTool. Pokud oříznutá oblast obsahovala text, nezapomeňte jej vložit do popisku souboru.

Jak zpracovat požadavek k extrakci: Nahrajte oříznutý obrázek jako nový soubor.

Příklad: Předtím, Potom

Nesvobodné rámečky

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

Viz také: Commons:Typy souborů

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

Viz také: Nápověda: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

Shortcut

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:Svobodné zdroje multimédií.

Versioning

For cleaned up media, a rule of thumb is to:

  1. first upload the original, dirty media;
  2. 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

  1. ↑ 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

English
German
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