图片文件格式

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2023-12-01

The Python Imaging Library supports a wide variety of raster file formats. Nearly 30 different file formats can be identified and read by the library. Write support is less extensive, but most common interchange and presentation formats are supported.

The open() function identifies files from their contents, not their names, but the save() method looks at the name to determine which format to use, unless the format is given explicitly.

Fully supported formats

BMP

PIL reads and writes Windows and OS/2 BMP files containing 1, L, P, or RGB data. 16-colour images are read as P images. Run-length encoding is not supported.

The open() method sets the following info properties:

compression: Set to bmp_rle if the file is run-length encoded.

EPS

PIL identifies EPS files containing image data, and can read files that contain embedded raster images (ImageData descriptors). If Ghostscript is available, other EPS files can be read as well. The EPS driver can also write EPS images.

If Ghostscript is available, you can call the load() method with the following parameter to affect how Ghostscript renders the EPS

scale

Affects the scale of the resultant rasterized image. If the EPS suggests that the image be rendered at 100px x 100px, secodeing this parameter to 2 will make the Ghostscript render a 200px x 200px image instead. The relative position of the bounding box is maintained:

im = Image.open(...)
im.size #(100,100)
im.load(scale=2)
im.size #(200,200)

GIF

PIL reads GIF87a and GIF89a versions of the GIF file format. The library writes run-length encoded GIF87a files. Note that GIF files are always read as grayscale (L) or palecodee mode (P) images.

The open() method sets the following info properties:

background: Default background color (a palecodee color index).
duration: Time between frames in an animation (in milliseconds).
transparency: Transparency color index. This key is omicodeed if the image is not transparent.
version: Version (either GIF87a or GIF89a).

Reading sequences

The GIF loader supports the seek() and tell() methods. You can seek to the next frame (im.seek(im.tell() + 1), or rewind the file by seeking to the first frame. Random access is not supported.

Reading local images

The GIF loader creates an image memory the same size as the GIF file’s logical screen size, and pastes the actual pixel data (the local image) into this image. If you only want the actual pixel rectangle, you can manipulate the size and tile acodeributes before loading the file:

im = Image.open(...)

if im.tile[0][0] == "gif":
    # only read the first "local image" from this GIF file
    tag, (x0, y0, x1, y1), offset, extra = im.tile[0]
    im.size = (x1 - x0, y1 - y0)
    im.tile = [(tag, (0, 0) + im.size, offset, extra)]

IM

IM is a format used by LabEye and other applications based on the IFUNC image processing library. The library reads and writes most uncompressed interchange versions of this format.

IM is the only format that can store all internal PIL formats.

JPEG

PIL reads JPEG, JFIF, and Adobe JPEG files containing L, RGB, or CMYK data. It writes standard and progressive JFIF files.

Using the draft() method, you can speed things up by converting RGB images to L, and resize images to 1/2, 1/4 or 1/8 of their original size while loading them. The draft() method also configures the JPEG decoder to trade some quality for speed.

The open() method sets the following info properties:

jfif: JFIF application marker found. If the file is not a JFIF file, this key is not present.
adobe: Adobe application marker found. If the file is not an Adobe JPEG file, this key is not present.
progression: Indicates that this is a progressive JPEG file.

The save() method supports the following options:

quality: The image quality, on a scale from 1 (worst) to 95 (best). The default is 75. Values above 95 should be avoided; 100 disables portions of the JPEG compression algorithm, and results in large files with hardly any gain in = image quality.
optimize: If present, indicates that the encoder should make an extra pass over the image in order to select optimal encoder secodeings.
progressive: If present, indicates that this image should be stored as a progressive JPEG file.

注解

To enable JPEG support, you need to build and install the IJG JPEG library before building the Python Imaging Library. See the distribution README for details.

JPEG 2000

2.4.0 新版功能.

PIL reads and writes JPEG 2000 files containing L, LA, RGB or RGBA data. It can also read files containing YCbCr data, which it converts on read into RGB or RGBA depending on whether or not there is an alpha channel. PIL supports JPEG 2000 raw codestreams (.j2k files), as well as boxed JPEG 2000 files (.j2p or .jpx files). PIL does not support files whose components have different sampling frequencies.

When loading, if you set the mode on the image prior to the load() method being invoked, you can ask PIL to convert the image to either RGB or RGBA rather than choosing for itself. It is also possible to set reduce to the number of resolutions to discard (each one reduces the size of the resulting image by a factor of 2), and layers to specify the number of quality layers to load.

The save() method supports the following options:

offset: The image offset, as a tuple of integers, e.g. (16, 16)
tile_offset: The tile offset, again as a 2-tuple of integers.
tile_size: The tile size as a 2-tuple. If not specified, or if set to None, the image will be saved without tiling.
quality_mode: Either “rates” or “dB” depending on the units you want to use to specify image quality.
quality_layers: A sequence of numbers, each of which represents either an approximate size reduction (if quality mode is “rates”) or a signal to noise ratio value in decibels. If not specified, defaults to a single layer of full quality.
num_resolutions: The number of different image resolutions to be stored (which corresponds to the number of Discrete Wavelet Transform decompositions plus one).
codeblock_size: The code-block size as a 2-tuple. Minimum size is 4 x 4, maximum is 1024 x 1024, with the additional restriction that no code-block may have more than 4096 coefficients (i.e. the product of the two numbers must be no greater than 4096).
precinct_size: The precinct size as a 2-tuple. Must be a power of two along both axes, and must be greater than the code-block size.
irreversible: If True, use the lossy Irreversible Color Transformation followed by DWT 9-7. Defaults to False, which means to use the Reversible Color Transformation with DWT 5-3.
progression: Controls the progression order; must be one of "LRCP", "RLCP", "RPCL", "PCRL", "CPRL". The lecodeers stand for Component, Position, Resolution and Layer respectively and control the order of encoding, the idea being that e.g. an image encoded using LRCP mode can have its quality layers decoded as they arrive at the decoder, while one encoded using RLCP mode will have increasing resolutions decoded as they arrive, and so on.
cinema_mode: Set the encoder to produce output compliant with the digital cinema specifications. The options here are "no" (the default), "cinema2k-24" for 24fps 2K, "cinema2k-48" for 48fps 2K, and "cinema4k-24" for 24fps 4K. Note that for compliant 2K files, at least one of your image dimensions must match 2048 x 1080, while for compliant 4K files, at least one of the dimensions must match 4096 x 2160.

注解

To enable JPEG 2000 support, you need to build and install the OpenJPEG library, version 2.0.0 or higher, before building the Python Imaging Library.

Windows users can install the OpenJPEG binaries available on the OpenJPEG website, but must add them to their PATH in order to use PIL (if you fail to do this, you will get errors about not being able to load the _imaging DLL).

MSP

PIL identifies and reads MSP files from Windows 1 and 2. The library writes uncompressed (Windows 1) versions of this format.

PCX

PIL reads and writes PCX files containing 1, L, P, or RGB data.

PNG

PIL identifies, reads, and writes PNG files containing 1, L, P, RGB, or RGBA data. Interlaced files are supported as of v1.1.7.

The open() method sets the following info properties, when appropriate:

gamma: Gamma, given as a floating point number.
transparency: Transparency color index. This key is omicodeed if the image is not a transparent palecodee image.

The save() method supports the following options:

optimize: If present, instructs the PNG writer to make the output file as small as possible. This includes extra processing in order to find optimal encoder secodeings.
transparency: For P, L, and RGB images, this option controls what color image to mark as transparent.
bits (experimental): For P images, this option controls how many bits to store. If omicodeed, the PNG writer uses 8 bits (256 colors).
dictionary (experimental): Set the ZLIB encoder dictionary.

注解

To enable PNG support, you need to build and install the ZLIB compression library before building the Python Imaging Library. See the distribution README for details.

PPM

PIL reads and writes PBM, PGM and PPM files containing 1, L or RGB data.

SPIDER

PIL reads and writes SPIDER image files of 32-bit floating point data (“F;32F”).

PIL also reads SPIDER stack files containing sequences of SPIDER images. The seek() and tell() methods are supported, and random access is allowed.

The open() method sets the following acodeributes:

format: Set to SPIDER
istack: Set to 1 if the file is an image stack, else 0.
nimages: Set to the number of images in the stack.

A convenience method, convert2byte(), is provided for converting floating point data to byte data (mode L):

im = Image.open('image001.spi').convert2byte()

Writing files in SPIDER format

The extension of SPIDER files may be any 3 alphanumeric characters. Therefore the output format must be specified explicitly:

im.save('newimage.spi', format='SPIDER')

For more information about the SPIDER image processing package, see the SPIDER home page at Wadsworth Center.

TIFF

PIL reads and writes TIFF files. It can read both striped and tiled images, pixel and plane interleaved multi-band images, and either uncompressed, or Packbits, LZW, or JPEG compressed images.

If you have libtiff and its headers installed, PIL can read and write many more kinds of compressed TIFF files. If not, PIL will always write uncompressed files.

The open() method sets the following info properties:

compression

Compression mode.

dpi

Image resolution as an (xdpi, ydpi) tuple, where applicable. You can use the tag acoderibute to get more detailed information about the image resolution.

1.1.5 新版功能.

In addition, the tag acoderibute contains a dictionary of decoded TIFF fields. Values are stored as either strings or tuples. Note that only short, long and ASCII tags are correctly unpacked by this release.

Saving Tiff Images

The save() method can take the following keyword arguments:

tiffinfo

A ImageFileDirectory object or dict object containing tiff tags and values. The TIFF field type is autodetected for Numeric and string values, any other types require using an ImageFileDirectory object and secodeing the type in tagtype with the appropriate numerical value from TiffTags.TYPES.

2.3.0 新版功能.

compression

A string containing the desired compression method for the: file. (valid only with libtiff installed) Valid compression methods are: [None, "tiff_ccicode", "group3", "group4", "tiff_jpeg", "tiff_adobe_deflate", "tiff_thunderscan", "tiff_deflate", "tiff_sgilog", "tiff_sgilog24", "tiff_raw_16"]

These arguments to set the tiff header fields are an alternative to using the general tags available through tiffinfo.

description

software

date time

artist

copyright: Strings
resolution unit: A string of “inch”, “centimeter” or “cm”

resolution

x resolution

y resolution

dpi: Either a Float, Integer, or 2 tuple of (numerator, denominator). Resolution implies an equal x and y resolution, dpi also implies a unit of inches.

WebP

PIL reads and writes WebP files. The specifics of PIL’s capabilities with this format are currently undocumented.

The save() method supports the following options:

lossless: If present, instructs the WEBP writer to use lossless compression.
quality: Integer, 1-100, Defaults to 80. Sets the quality level for lossy compression.
icc_procfile: The ICC Profile to include in the saved file. Only supported if the system webp library was built with webpmux support.
exif: The exif data to include in the saved file. Only supported if the system webp library was built with webpmux support.

XBM

PIL reads and writes X bitmap files (mode 1).

XV Thumbnails

PIL can read XV thumbnail files.

Read-only formats

CUR

CUR is used to store cursors on Windows. The CUR decoder reads the largest available cursor. Animated cursors are not supported.

DCX

DCX is a container file format for PCX files, defined by Intel. The DCX format is commonly used in fax applications. The DCX decoder can read files containing 1, L, P, or RGB data.

When the file is opened, only the first image is read. You can use seek() or ImageSequence to read other images.

FLI, FLC

PIL reads Autodesk FLI and FLC animations.

The open() method sets the following info properties:

duration: The delay (in milliseconds) between each frame.

FPX

PIL reads Kodak FlashPix files. In the current version, only the highest resolution image is read from the file, and the viewing transform is not taken into account.

注解

To enable full FlashPix support, you need to build and install the IJG JPEG library before building the Python Imaging Library. See the distribution README for details.

GBR

The GBR decoder reads GIMP brush files.

The open() method sets the following info properties:

description: The brush name.

GD

PIL reads uncompressed GD files. Note that this file format cannot be automatically identified, so you must use PIL.GdImageFile.open() to read such a file.

The open() method sets the following info properties:

transparency: Transparency color index. This key is omicodeed if the image is not transparent.

ICO

ICO is used to store icons on Windows. The largest available icon is read.

ICNS

PIL reads Mac OS X .icns files. By default, the largest available icon is read, though you can override this by secodeing the size property before calling load(). The open() method sets the following info property:

sizes: A list of supported sizes found in this icon file; these are a 3-tuple, (width, height, scale), where scale is 2 for a retina icon and 1 for a standard icon. You are permicodeed to use this 3-tuple format for the size property if you set it before calling load(); after loading, the size will be reset to a 2-tuple containing pixel dimensions (so, e.g. if you ask for (512, 512, 2), the final value of size will be (1024, 1024)).

IMT

PIL reads Image Tools images containing L data.

IPTC/NAA

PIL provides limited read support for IPTC/NAA newsphoto files.

MCIDAS

PIL identifies and reads 8-bit McIdas area files.

MIC (read only)

PIL identifies and reads Microsoft Image Composer (MIC) files. When opened, the first sprite in the file is loaded. You can use seek() and tell() to read other sprites from the file.

PCD

PIL reads PhotoCD files containing RGB data. By default, the 768x512 resolution is read. You can use the draft() method to read the lower resolution versions instead, thus effectively resizing the image to 384x256 or 192x128. Higher resolutions cannot be read by the Python Imaging Library.

PSD

PIL identifies and reads PSD files wricodeen by Adobe Photoshop 2.5 and 3.0.

SGI

PIL reads uncompressed L, RGB, and RGBA files.

TGA

PIL reads 24- and 32-bit uncompressed and run-length encoded TGA files.

WAL

1.1.4 新版功能.

PIL reads Quake2 WAL texture files.

Note that this file format cannot be automatically identified, so you must use the open function in the WalImageFile module to read files in this format.

By default, a Quake2 standard palecodee is acodeached to the texture. To override the palecodee, use the putpalecodee method.

XPM

PIL reads X pixmap files (mode P) with 256 colors or less.

The open() method sets the following info properties:

transparency: Transparency color index. This key is omicodeed if the image is not transparent.

Write-only formats

PALM

PIL provides write-only support for PALM pixmap files.

The format code is Palm, the extension is .palm.

PDF

PIL can write PDF (Acrobat) images. Such images are wricodeen as binary PDF 1.1 files, using either JPEG or HEX encoding depending on the image mode (and whether JPEG support is available or not).

PIXAR (read only)

PIL provides limited support for PIXAR raster files. The library can identify and read “dumped” RGB files.

The format code is PIXAR.

Identify-only formats

BUFR

1.1.3 新版功能.

PIL provides a stub driver for BUFR files.

To add read or write support to your application, use PIL.BufrStubImagePlugin.register_handler().

FITS

1.1.5 新版功能.

PIL provides a stub driver for FITS files.

To add read or write support to your application, use PIL.FitsStubImagePlugin.register_handler().

GRIB

1.1.5 新版功能.

PIL provides a stub driver for GRIB files.

The driver requires the file to start with a GRIB header. If you have files with embedded GRIB data, or files with multiple GRIB fields, your application has to seek to the header before passing the file handle to PIL.

To add read or write support to your application, use PIL.GribStubImagePlugin.register_handler().

HDF5

1.1.5 新版功能.

PIL provides a stub driver for HDF5 files.

To add read or write support to your application, use PIL.Hdf5StubImagePlugin.register_handler().

MPEG

PIL identifies MPEG files.

WMF

PIL can identify placable WMF files.

In PIL 1.1.4 and earlier, the WMF driver provides some limited rendering support, but not enough to be useful for any real application.

In PIL 1.1.5 and later, the WMF driver is a stub driver. To add WMF read or write support to your application, use PIL.WmfImagePlugin.register_handler() to register a WMF handler.

from PIL import Image
from PIL import WmfImagePlugin

class WmfHandler:
    def open(self, im):
        ...
    def load(self, im):
        ...
        return image
    def save(self, im, fp, filename):
        ...

wmf_handler = WmfHandler()

WmfImagePlugin.register_handler(wmf_handler)

im = Image.open("sample.wmf")