84 lines
2.8 KiB
Groff
84 lines
2.8 KiB
Groff
.TH IM_JPEG2VIPS 3 "6 June 1994"
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.SH NAME
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im_jpeg2vips, im_vips2jpeg, im_vips2bufjpeg, im_vips2mimejpeg \- convert JPEG images to and from VIPS format
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_jpeg2vips( char *filename, IMAGE *out )
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int im_jpeg2vips_header( char *filename, IMAGE *out )
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int im_vips2jpeg( IMAGE *in, char *filename )
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int im_vips2bufjpeg( IMAGE *in, IMAGE *base, char **obuf, int *olen )
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int im_vips2mimejpeg( IMAGE *in )
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.SH DESCRIPTION
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.B im_jpeg2vips()
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reads the named jpeg file and writes it to the specified
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IMAGE. The entire image is read before returning. It can read most 8-bit JPEG
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images, including CMYK.
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You can embed options in the filename. They have the form:
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filename.jpg:<shrink-factor>
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.B shrink-factor
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will shrink the image by that factor during read. Allowed values are 1, 2, 4
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and 8. Shrinking during read is very much faster than decompressing the whole
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image and then shrinking. Example:
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fred.jpg:8
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will return fred.jpg shrink by a factor of 8.
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Any embedded ICC profiles are ignored: you always just get the RGB from the
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file. Instead, the embedded profile will be attached to the image as metadata.
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Any EXIF data is also attached as VIPS metadata.
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.B im_jpeg2vips_header()
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reads just the header of the JPEG file (including any EXIF data), and sets
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the fields in the VIPS image.
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You can't read any pixels! This is only useful for printing header
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information.
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.B im_vips2jpeg()
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writes the IMAGE to filename in JPEG format. It uses the
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default settings of the IJG library.
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A compression factor may be encoded in the filename: for example,
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"fred.jpg" will write with the default compression factor (75),
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"fred.jpg:25" will write with factor 25.
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An ICC profile may also be specified. For example,
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"fred.jpg:25,/home/john/srgb.icc" will embed the profile stored in the file
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"/home/john/srgb.icc" into the JPEG image. This does not affect the pixels
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which are written; just the way they are tagged.
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If no profile is specified in the save string and the VIPS header contains an
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ICC profile named IM_META_ICC_NAME ("icc-profile-data"), the
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profile from the header will be attached.
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The image is automatically converted to RGB or Monochrome before saving. Any
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metadata attached to the image is saved as EXIF, if possible.
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.B im_vips2bufjpeg()
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returns the compressed image in a memory buffer. The buffer
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is allocated for you, local to IMAGE descriptor
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.B base.
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The size of the
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allocated buffer is returned in the
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.B olen
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parameter. You are responsible for
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freeing the buffer. The buffer is only allocated if the function returns
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successfully.
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.B im_vips2mimejpeg()
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writes the image to stdout as a MIME image/jpeg type. It
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outputs Content-Length and Content-Type fields making the result suitable for
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sending to a web browser.
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.SH SEE ALSO
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im_isjpeg(3).
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