JPEG (.jpg, .jpeg)

Background & Context

    • MIME type: image/jpeg
    • JPEG raster image and compression format.
    • Commonly used for photographic images by digital cameras and on the web.
    • JPEG is an acronym for Joint Photographic Experts Group.
    • Supports Grayscale, RGB, and CMYK color spaces.
    • Stores images as bitmaps at a resolution of 8 bits per color channel.
    • Binary format.
    • Uses a lossy compression method based on an 8×8 block-sized discrete cosine transform.
    • Supports different compression levels.

Import & Export

  • Import["file.jpg"] imports a JPEG file, returning an image.
  • Import["file.jpg",elem] imports the specified element from a JPEG file.
  • The import format can be specified with Import["file","JPEG"] or Import["file",{"JPEG",elem,}].
  • Export["file.jpg",expr] exports an image, graphics, or any other expression as an image to a JPEG file.
  • Image objects are by default exported at their full raster size. Graphics and other arbitrary expressions are exported using the same raster size as their displayed form.
  • See the reference pages for full general information on Import and Export.
  • ImportString and ExportString support the JPEG format.

Notebook Interface

  • In the notebook front end, Insert Picture and the Open menu allow the import of a JPEG file into a cell.
  • Save Selection As exports the selected part of a notebook as a JPEG file.

Import Elements

  • General Import elements:
  • "Elements" list of elements and options available in this file
    "Rules"full list of rules for each element and option
    "Options"list of rules for options, properties, and settings
  • Data representation elements:
  • "ColorMap"color reduction palette
    "Data"array of pixel values
    "Graphics"raster image, given as a Graphics object
    "Image"raster image, given as an Image object
    "RawData"array of color map indices
    {"Thumbnail",size}thumbnail of the first image (default size = Small)
  • Import and Export by default use the "Image" element for the JPEG format.
  • Advanced Import elements:
  • "BitDepth"bits used to represent each color channel in the file
    "CameraTopOrientation"orientation of the camera when the picture was taken
    "Channels"
  • the number of color channels used in the file
  • "ColorProfileData"embedded color profile, given as a ColorProfileData object
    "ColorSpace"color encoding used in the file
    "FlashUsed"
  • whether the flash was fired
  • "GeoPosition"latitude and longitude represented as a GeoPosition object
    "GPSDateTime"
  • image creation date and time registered by GPS
  • "ImageSize"raster dimensions
    "RedEyeCorrection"whether a red-eye correction was performed
    "Summary"
  • summary of the file
  • Metadata elements:
  • "Exif"formatted Exif (Exchange image file format)
    "IPTC"formatted IPTC (International Press Telecommunications Council)
    "XMP"formatted XMP (Extensible metadata platform)
  • Raw metadata, as stored in the file, can be imported using "RawExif", "RawXMP" and "RawIPTC" elements which are returned in an association.
  • All Exif and IPTC tags can be imported individually. Common tags include:
  • "ApertureValue"lens aperture
    "Artist"photographer or image creator
    "DateTime"image creation date and time
    "ExposureTime"exposure time, given in seconds
    "FlashInfo"
  • flash information: flash fired, red-eye correction, etc.
  • "FNumber"F number
    "FocalLength"actual focal length of the lens, given in millimeters
    "GPSAltitude"altitude of the GPS position
    "GPSLatitude"latitude of the GPS position
    "GPSLongitude"longitude of the GPS position
    "Make"manufacturer of the recording equipment
    "Model"model name or model number of the equipment
    "Software"name and version of the software or firmware of the camera or image input device used to generate the image

Options

  • Import and Export options:
  • ImageResolutionAutomaticresolution values for import and export
    ImageSizeAutomaticoverall image size
    IncludeMetaInformationAllmetadata types to import and export
    "ImageTopOrientation"Automaticorientation of the image as stored in the file
  • Import option:
  • "TakeRows"{1,-1}rows to import
  • Export options:
  • "ColorSpace""RGB"color encoding to be used in the file
    CompressionLevel0.25sets the JPEG compression parameter
    "Progressive"Falsewhether to store the image in a way that allows progressive display while the file is being loaded
    "Smoothing"0the JPEG smoothing parameters, given as a number in the range 0 (no smoothing) to 1
    ImageFormattingWidth$ImageFormattingWidthtarget width when formatting an object
  • Supported "ColorSpace" settings are: "Grayscale", "RGB", and "CMYK". Using "ColorSpace"->Automatic, Export attempts to create a JPEG file with the same color space.
  • The value of CompressionLevel can be in the range from 0 to 1, with larger values resulting in smaller file sizes but lower-quality encodings.

Examples

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Basic Examples  (3)

Import a JPEG image as an image:

Summary of an image:

Export an RGB image to JPEG:

Scope  (3)

Import the image as a graphics:

Import Exif metadata:

Import a metadata element:

Import multiple metadata elements:

Import Elements  (34)

Available Elements  (5)

List of available elements:

List of available Exif elements:

List of available IPTC elements:

Get image-related information as list of rules:

Import some image options:

The "Options" element does not return all options that are present in the imported image:

Data Representation  (7)

"ColorMap"  (2)

Get the color-reduction palette created on import:

Visualize the color-reduction palette:

Apply the color map to the raw data to create the stored image:

"Data"  (1)

Import the image data:

Create an image from imported data:

"Graphics"  (1)

Import as a Graphics object:

"Image"  (1)

Import as an Image object:

This is the default import element for JPEG:

"RawData"  (1)

Get the raw data:

Plot the array of raw data:

Use the color map to create the stored image:

"Thumbnail"  (1)

Import a thumbnail of an image:

Specify the thumbnail size:

Metadata  (22)

"BitDepth"  (1)

Get the bit count for the representation of each color channel:

"CameraTopOrientation"  (2)

Get the camera orientation at the capture time:

The image is auto-rotated on Import:

An auto-rotated image has an updated Exif tag:

Avoid auto-rotation by setting the "ImageTopOrientation" option:

"Channels"  (1)

Get the number of image channels:

"ColorProfileData"  (1)

Get the embedded color profile, given as a ColorProfileData object:

The color profile is stored in the ColorSpace option of the imported image:

"ColorSpace"  (1)

Get the color encoding used on export:

Use ImageColorSpace to get the color space of an imported image:

"DateTime"  (1)

Get the date and time that the image was captured:

"Exif"  (3)

Get Exif metadata:

Extract an individual tag from the association:

Individual Exif tags can also be imported directly:

Some Exif tags are processed to give more detailed information:

Compare with the raw "FlashInfo" tag:

"FlashUsed"  (1)

Import a tag that shows whether the flash fired:

"FlashUsed" is a subelement of the "FlashInfo" element:

Extract "FlashUsed" from the full "Exif":

"GeoPosition"  (2)

Import an image geo position:

Use the image thumbnail as the marker:

The image geo position may be unavailable:

"GPSDateTime"  (1)

Get the image creation date and time registered by GPS:

"ImageSize"  (1)

Get the dimensions of the image stored in the file:

Using ImageDimensions on an imported image gives the same result:

"IPTC"  (1)

Get IPTC metadata:

"RawExif"  (1)

Import raw Exif data:

When importing processed Exif data, missing tags are removed:

Raw Exif tags return the actual values stored in the file:

When importing "Exif", most tags are processed:

"RawIPTC"  (1)

Import unprocessed IPTC metadata:

When importing processed IPTC, missing tags are automatically removed:

"RawXMP"  (1)

Import unprocessed XMP metadata:

When importing processed XMP, missing tags are automatically removed:

"RedEyeCorrection"  (1)

Whether a red-eye correction was performed:

"Summary"  (1)

Get the image summary:

"XMP"  (1)

Get XMP metadata:

Extract the XMP "BasicSchema" metadata:

Import Options  (7)

ImageResolution  (1)

By default, the image resolution is extracted from the file:

Specify the resolution of the imported image:

Specify different resolutions in and directions:

ImageSize  (1)

By default, images are imported in their full resolution:

Specify the raster size of the imported JPEG image:

"ImageTopOrientation"  (1)

By default, images are imported with the native orientation stored in the file:

Specify the side that is supposed to be on the top:

The correct orientation can also be achieved by rotating the image to be upright:

IncludeMetaInformation  (3)

By default, all available metadata is imported:

Possible classes of metadata for JPEG files are "Exif", "IPTC", and "XMP":

Import the image with no metadata:

Import the image with "XMP" metadata only:

"TakeRows"  (1)

By default, all rows are imported:

Import only the specified rows:

Export Options  (7)

"ColorSpace"  (1)

By default, the native color space of the image is used for export:

Export as a CMYK image:

CompressionLevel  (2)

By default, an automatic compression is used:

Use maximum compression:

Use minimum compression:

Compare the byte count for different compression levels:

ImageSize  (1)

By default, the image is exported in the full resolution:

Specify the raster size of exported image:

ImageResolution  (1)

By default, the original image resolution is used during export:

Specify the resolution of the exported image:

"ImageTopOrientation"  (1)

By default, the upright image is exported using "ImageTopOrientation"->Top:

Specify the orientation:

IncludeMetaInformation  (1)

By default, all existing meta-information is exported:

Specify the metadata to include:

Export no metadata:

Introduced in 1999
 (4.0)
 |
Updated in 2016
 (11.0)