Difference between revisions of "Help:Images"
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Revision as of 14:36, 30 August 2018
This page explains the image syntax when editing theKnowledge Management system. You or another user must usually upload an image before you can use it on a page.
Images that are stored on aKnowledge Management systemserver are usually rendered by using the File: namespace prefix (but the legacy Image: namespace prefix is still supported as a synonym) as the target of aKnowledge Management systemlink. The alternate Media: namespace prefix is also usable to reference the original media file content (for rendering or downloading it separately, out of anyKnowledge Management systempage).
Supported media types for images
The following file formats are supported by default:
- .jpg or .jpeg : bitmap image compressed in the standard JPEG format (this lossy format is most suitable for photographs).
- .png : bitmap image in the Portable Network Graphics format (specified by the W3 Consortium).
- .gif : bitmap image in the legacy Graphics Interchange Format.
Other formats used onKnowledge Management systemmedia, and commonly enabled elsewhere (these may require extra set-up beyond what is enabled by default):
- .svg : scalable image in the Scalable Vector Graphics format (specified by the W3 Consortium).
- .tiff : Tagged image format. Often used for high-resolution archival photographs. Often used with
- .ogg, .oga, .ogv : Ogg multimedia (audio or video). Not an image format, but treated similarly. Often used with
- .pdf : multipaged documents in the Portable Document Format (initially specified by Adobe). Often used in conjunction with
- .djvu : multipaged bitmap documents in the DejaVu format (most often, scans of books).
- Only a single page of a .pdf or .djvu file is shown at one time.
Only a single page of a .pdf or .djvu file is shown at one time.
Other media types may be supported, but it may not be possible to display them inline.
Rendering a single image
Syntax
The full syntax for displaying an image is:
[[File:<i>filename.extension</i>|<i>options</i>|<i>caption</i>]]
where options can be zero or more of the following, separated by pipes (|):
- Format option: one of border and/or frameless, frame, thumb (or thumbnail);
- Controls how the rendered image is formatted and embedded in the rest of the page.
- Resizing option: one of
- {width}px — Resizes the image to fit within the given maximum width in pixels, without restricting its height;
- x{height}px — Resizes the image to fit within the given maximum height in pixels, without restricting its width;
- {width}x{height}px — Resizes the image to fit within the given width and height in pixels;
- upright — Resizes an image to fit within reasonable dimensions, according to user preferences (suitable for images whose height is larger than width).
- Note that the image will always retain its aspect ratio, and can only be reduced (not increased) in size unless it's in a scalable media type (bitmap images cannot be scaled up).
- The default maximum size depends on the format and the internal image dimensions (according to its media type).
- Horizontal alignment option: one of left, right, center, none;
- Controls the horizontal alignment (and inline/block or floating styles) of the image within a text (no default value).
- Vertical alignment option: one of baseline, sub, super, top, text-top, middle, bottom, text-bottom;
- Controls the vertical alignment of a non-floating inline image with the text before or after the image, and in the same block (the default vertical alignment is middle).
- Link option: one of
- link={target} — Allows to change the target (to an arbitrary page title, or URL) of the generated link, activable on the rendered image surface; e.g.
20pxrenders as
(external link), or 20pxrenders as (internal link). - link= (with an empty value) — Displays an image without any activable link; e.g.
20pxrenders as.
- ! for MW 1.24 and lower: If you set
|link=|(empty), then notitlewill be rendered.
- ! for MW 1.24 and lower: If you set
- link={target} — Allows to change the target (to an arbitrary page title, or URL) of the generated link, activable on the rendered image surface; e.g.
- Other specific options:
- alt={alternative text} — Defines the alternative text (maps to the HTML attribute
alt="..."of the generated<img />element) of an image that will be rendered if either the referenced image cannot be downloaded and embedded, or if the support media must use the alternative description text (e.g. when using a Braille reader or with accessibility options set by the user in its browser). - page={number} — Renders the specified page number (currently only applicable when showing a .djvu or .pdf file).
- class={html class} — (Knowledge Management system1.20+) Defines classes (maps to the HTML attribute
class="..."of the generated<img />element). - lang={language code} — (Knowledge Management system1.22+) For SVG files containing <switch> statements varying on a systemLanguage attribute, selects what language to render the file in. The default is always English, even on non-EnglishKnowledge Management systems.
- alt={alternative text} — Defines the alternative text (maps to the HTML attribute
If a parameter does not match any of the other possibilities, it is assumed to be the caption text. Caption text shows below the image in thumb and frame formats, or as tooltip text in any other format. Caption text displayed in the thumb and frame formats may containKnowledge Management system links and other formatting.Knowledge Management systemextensions can add additional options.
If 'alt' is not specified and a caption is provided, the alternative text will be created automatically from the caption, stripped of formatting, except when in thumb or frame mode since the caption is already readable by screen readers in that case.
Format
The following table shows the effect of all available formats.
| Description | You type | You get |
|---|---|---|
| no format specified Rendered as a floating block: no Rendered inline: yes Rendered caption: no |
... text text text [[File:example.jpg|caption]] text text text ... |
... text text text
|
| border results in a very small gray border Rendered as a floating block: no Rendered inline: yes Rendered caption: no |
... text text text [[File:example.jpg|<b>border</b>|caption]] text text text ... |
... text text text
|
| frameless, like thumbnail, respect user preferences for image width, but without border and no right float Rendered as a floating block: no Rendered inline: yes Rendered caption: no |
... text text text [[File:example.jpg|<b>frameless</b>|caption]] text text text ... |
... text text text
|
| frameless and border Rendered as a floating block: no Rendered inline: yes Rendered caption: no |
... text text text [[File:example.jpg|<b>frameless</b>|<b>border</b>|caption]] text text text ... |
... text text text
|
| frame Rendered as a floating block: yes Rendered inline: no Rendered caption: yes |
... text text text [[File:example.jpg|<b>frame</b>|caption]] text text text ... |
... text text text
 caption text text text ... |
| thumb or thumbnail Rendered as a floating block: yes Rendered inline: no Rendered caption: yes |
... text text text [[File:example.jpg|<b>thumb</b>|caption]] text text text ... |
... text text text
 caption text text text ... |
| Format | Reduced | Enlarged |
|---|---|---|
| (not specified) |
[[File:Example.jpg|<b>50px</b>]]
|
[[File:Example.jpg|<b>200px</b>]]
|
| border |
[[File:Example.jpg|border|<b>50px</b>]]
|
[[File:Example.jpg|border|<b>200px</b>]]
|
| frame |
[[File:Example.jpg|frame|<b>50px</b>]] |
[[File:Example.jpg|frame|<b>200px</b>]]
|
| thumb |
[[File:Example.jpg|thumb|<b>50px</b>]]  |
[[File:Example.jpg|thumb|<b>200px</b>]] 
|
| frameless |
[[File:Example.jpg|frameless|<b>50px</b>]]
|
[[File:Example.jpg|frameless|<b>200px</b>]]
|
Horizontal alignment
Note that when using the frame or thumb[nail] formats, the default horizontal alignment will be right.
| Description | You type | You get |
|---|---|---|
| no horizontal alignment specified, or default alignment Rendered as a floating block: no Rendered inline: yes |
... text text text [[File:example.jpg|<b>100px</b>|caption]] text text text ... |
... text text text
|
| specify horizontal alignment as: none Rendered as a floating block: no Rendered inline: no |
... text text text [[File:example.jpg|<b>none</b>|<b>100px</b>|caption]] text text text ... |
... text text text
 text text text ... |
| specify horizontal alignment as: center Rendered as a floating block: no Rendered inline: no |
... text text text [[File:example.jpg|<b>center</b>|<b>100px</b>|caption]] text text text ... |
... text text text
text text text ... |
| specify horizontal alignment as: left Rendered as a floating block: yes Rendered inline: no |
... text text text [[File:example.jpg|<b>left</b>|<b>100px</b>|caption]] text text text ... |
... text text text
text text text ... |
| specify horizontal alignment as: right Rendered as a floating block: yes Rendered inline: no |
... text text text [[File:example.jpg|<b>right</b>|<b>100px</b>|caption]] text text text ... |
... text text text
text text text ... |
Vertical alignment
The vertical alignment options take effect only if the image is rendered as an inline element and is not floating. They alter the way the inlined image will be vertically aligned with the text present in the same block before and/or after this image on the same rendered row.
Note that the rendered line of text where inline images are inserted (and the lines of text rendered after the current one) may be moved down (this will increase the line-height conditionally by additional line spacing, just as it may occur with spans of text with variable font sizes, or with superscripts and subscripts) to allow the image height to be fully displayed with this alignment constraint.
To show the alignment result more clearly, the text spans are overlined and underlined, the font-size is increased to 200%, and the paragraph block is outlined with a thin border; additionally images of different sizes are aligned:
text
top: 
text
text
text-top:
text
text
super:
text
text
baseline:
text
text
sub:
text
text
default:
text
text
middle:
text
text
text-bottom:
text
text
bottom:
text
Notes:
- The "middle" vertical alignment position of the image (which is also the default) usually refers to the middle between the x-height and the baseline of the text (on which the vertical middle of the image will be aligned, and on which usually the text may be overstroke), but not to the middle of the line-height of the font-height that refers to the space between the "text-top" and "text-bottom" positions ; the font-height excludes:
- the additional line separation spacing normally divided equally into two line-margins (here 0.5em, according to line-height set to 200%) above and below the font-height).
- the additional line spacing which may be added by superscripts and subscripts.
- However, if the image height causes its top or bottom position to go above or below the normal full line-height of text, the middle position will be adjusted after the increasing the top and/or bottom line-margins so that the image can fit and align properly, and all images (including those with smaller heights) will be vertically centered on the adjusted middle position (for computing the effective line-height, the text of each rendered row with the larger font-height will be considered).
- The "text-top" and "text-bottom" alignment positions also excludes the extra line spacing added by superscripts and subscripts, but not the additional line-spacing defined by the line-height.
- The "top" and "bottom" alignment positions take into account all these extra line spacings (including superscripts and subscripts, if they are present in a rendered line span). When the image alignment constrains the image to grow above or below the normal line-spacing, and the image is not absolutely positioned, the image will cause the "top" and "bottom" positions to be adjusted (just like superscripts and subscripts), so the effective line-height between rendered lines of text will be higher.
- The "underline", "overline" and "overstrike" text-decoration positions should be somewhere within these two limits and may depend on the type and height of fonts used (the superscript and subscript styles may be taken into account in some browsers, but usually these styles are ignored and the position of these decorations may not be adjusted); so these decorations normally don't affect the vertical position of images, relatively to the text.
Stopping the text flow
On occasion it is desirable to stop text (or other inline non-floating images) from flowing around a floating image. Depending on the web browser's screen resolution and such, text flow on the right side of an image may cause a section header (for instance, == My Header ==) to appear to the right of the image, instead of below it, as a user may expect. The text flow can be stopped by placing(or if you prefer, ) before the text that should start below the floating image. (This may also be done without an empty line by wrapping the section with the floating images with , which clears all floats inside the div element.)
All images rendered as blocks (including non-floating centered images, left- or right-floating images, as well as framed or thumbnailed floating images) are implicitly breaking the surrounding lines of text (terminating the current block of text before the image, and creating a new paragraph for the text after them). They will then stack vertically along their left or right alignment margin (or along the center line between these margins for centered images).
Altering the default link target
The following table shows how to alter the link target (whose default is the image description page) or how to remove it. Changing the link does not alter the format described in the previous sections.
| Description | You type | You get |
|---|---|---|
| internal link |
... text text text [[File:example.jpg|<b>link=Main Page</b>|caption]] text text text ... |
... text text text
|
| external link |
... text text text [[File:example.jpg|<b></b>|caption]] text text text ... |
... text text text
|
| no link (external or file page) |
... text text text [[File:example.jpg|<b>link=</b>|caption]] text text text ... |
... text text text
|
Warning:
The licencing requirements on yourKnowledge Management system may not allow you to remove all links to the description page that displays the required authors attributions, the copyrights statements, the applicable licencing terms, or a more complete description of the rendered image (including its history of modifications). If you change or remove the target link of an image, you will then have to provide somewhere else on your page an explicit link to this description page, or to display the copyright and author statement and a link to the applicable licence, if they are different from the elements applicable to the embedding page itself. YourKnowledge Management system policy may restrict the use of the alternate link parameter, or may even enforce a prohibition of alternate link parameters for embedded media files (in which case, the link parameter will be ignored), or may only accept them after validation by authorized users or administrators.