Editing Pixel density (section)

== Image file format support ==

The following table show how pixel density is supported by popular image file formats. The cell colors used do not indicate how feature-rich a certain image file format is, but what density support can be expected of a certain image file format.

Even though image manipulation software can optionally set density for some image file formats, not many other software uses density information when displaying images. Web browsers, for example, ignore any density information. As the table shows, support for density information in image file formats varies enormously and should be used with great care in a controlled context.<!-- Named pixel densities is used mainly for browsers and mobile apps. -->

{| class="sortable wikitable" style="text-align:center; width:auto; font-size:smaller;"
|- <!--Often-used image file formats that do not support pixel density are added for counter-example purposes.-->
! style="width:7em;" | Format
! [[Units of measurement]]{{efn|''Length'' refers to horizontal and vertical size in inches, centimeters, etc., whereas ''pixel'' refers only to the number of pixels found along the horizontal and vertical dimension.}}
! [[raster graphics|Raster]]/[[Vector graphics|vector]]
! Multi-page
! Per-page size
! Size in lengths for image or page
! Density
|-
![[Exif]]
|Length
|Raster
|
|
|
|PPI or PPCM, 8 bytes (64bit rational unsigned) each for horizontal and vertical directions<ref>Exif 2.32, CIPA DC-008 Translation 2019, p.35-36</ref>
|-
! [[Adobe Illustrator Artwork|AI]]
| Length or pixel
| Both
| colspan=2 {{No}}
| {{yes|Explicit for length. No for pixel}}
| {{partial|Implicit for included raster images}}
|-
! [[Encapsulated PostScript|EPS]]
| Length
| Both
| {{Yes}}
| {{Yes}}
| {{yes|Explicit}}
| {{partial|Explicit DPI (PPI) for rasterized images, fonts or effects}}
|-
! [[GIF]]
| Pixel
| Raster
| {{Yes}}
| {{No}}
| {{no}}
| {{no}}
|-
! [[ICO (file format)|ICO]]
| Pixel
| Raster
| {{Yes}}
| {{Yes}}
| {{no}}
| {{no}}
|-
! [[JPEG]]
| Pixel
| Raster
| colspan=2 {{No}}
| {{partial|Implicit when density is set}}
| {{partial|Optional PPI or PPCM, 2 bytes each for horizontal and vertical directions<ref>[https://www.w3.org/Graphics/JPEG/jfif3.pdf JPEG File Interchange Format, Version 1.02 - JPEG File Interchange Format Specification]</ref>}}
|-
! [[PDF]]
| Length
| Both
| {{Yes}}
| {{Yes}}
| {{yes|Explicit}}
| {{partial|Explicit DPI (PPI) for rasterized images, fonts or effects}}
|-
! [[Portable Network Graphics|PNG]]
| Pixel
| Raster
| colspan=2 {{No}}
| {{partial|Implicit when density is set}}
| {{partial|Optional PPM, 4 bytes each horizontal and vertical directions<ref>[http://www.libpng.org/pub/png/book/chapter11.html#png.ch11.div.8 Chapter 11. PNG Options and Extensions - Physical Pixel Dimensions (pHYs)]</ref>}}
|-
! [[Portable pixmap|PPM]]
| Pixel
| Raster
| {{Yes}}
| {{No}}
| {{no}}
| {{no}}
|-
! [[Adobe Photoshop|PSD and PSB]]
| Length or pixel
| Both
| colspan=2 {{No}}
| {{yes|Explicit for length. No for pixel}}
| {{partial|Optional}}
|-
! [[Scalable Vector Graphics|SVG]]
| Length or pixel
| Both
| {{Yes}}
| {{No}}
| {{partial|Explicit for length.{{efn|Support in SVG differs. The standard supports the floats pixelUnitToMillimeterX, pixelUnitToMillimeterY, screenPixelToMillimeterX and screenPixelToMillimeterY for use in [[Cascading Style Sheets#CSS 2|CSS2]].<ref>[https://www.w3.org/TR/SVG/single-page.html Scalable Vector Graphics (SVG) 1.1 (Second Edition)]</ref> Inkscape SVG supports density for PNG export only inkscape:export-xdpi and inkscape:export-ydpi.<ref>[https://bazaar.launchpad.net/~inkscape.dev/inkscape/trunk/files Inkscape source files]</ref> Adobe stores it even differently.
}} No for pixel}}
| {{partial|Implicit for included raster images}}
|-
! [[Tagged Image File Format|TIFF]]
| Pixel
| Both
| {{Yes}}
| {{Yes}}
| {{partial|Implicit when density is set}}
| {{partial|Optional PPI or PPCM, two 32-bit unsigned integers each for horizontal and vertical directions<ref>[http://cool.conservation-us.org/bytopic/imaging/std/tiff5.html TIFF Revision 5.0 - ResolutionUnit]</ref>}}
|-
! [[WebP]]
| Pixel
| Raster
| {{Yes}}
| {{unknown}}
| {{unknown}}
|{{partial|WEBP has no tags/attributes of its own which specify density on the output medium. But WEBP uses [[Resource Interchange File Format]] as its container format which [https://developers.google.com/speed/webp/docs/riff_container#metadata supports Metadata to be included as XMP and EXIF chunks]. And EXIF supports resolution, see entry in this table. Practical example: [[GraphicConverter]] v11.7.1 correctly shows resolution information for WEBP files with EXIF metadata.}}
|-
! [[XCF (file format)|XCF]]
| Pixel
| Both
| colspan=2 {{No}}
| {{no}}
| {{partial|Optional PPI, 32-bit float each for horizontal and vertical directions<ref>[https://developer.gimp.org/core/standards/xcf/ Documentation of the XCF file format]</ref>}}
|- class="sortbottom"
! style="width:7em;" | Format
! [[Units of measurement]]
! [[raster graphics|Raster]]/[[Vector graphics|vector]]
! Multi-page
! Per-page size
! Size in lengths for image or page
! Density
|}

{{noteslist}}