Hi,
is there a way that I can force GM not to generate any temporary files at all?
My goal is to pipe image files to and from GM (via stdio) as fast as possible without putting load onto the hard drive.
Thanks in advance
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Hi,
is there a way that I can force GM not to generate any temporary files at all?
My goal is to pipe image files to and from GM (via stdio) as fast as possible without putting load onto the
hard drive.
Temporary files are used for several purposes. For huge images where
the decoded representation can't fit entirely in memory, disk files
are used to support the "pixel cache". When external programs are
used (e.g. Ghostscript) these programs may require use of temporary
files to pass input data and obtain output data. When input is piped
from stdio then if the coder (reader) for the input format is declared
to need to be able to seek in the input stream (MagickInfo
seekable_stream is set to True), then it is necessary to buffer the
input from stdio to a temporary file since pipes do not support
seek().
For some formats (e.g. TIFF), using seek is unavoidable. For some
other formats, seek was used due to the programmer being lazy or due
to some notion of efficiency (skip over rather than read).
These formats are currently declared as requiring seek:
In order to support automatic file type identification (in case it is
not already specified), GraphicsMagick reads the first part of the
file data to determine the file format and then rewinds the file
descriptor to the beginning of the file before invoking the correct
decoder. It is not possible to rewind the file descriptor on a pipe.
It is possible to buffer that input for subsequent re-use but this has
not yet been implemented. For these cases, explicitly specifying the
file format will avoid use of a temporary file:
For example, without specifying the input format, '-debug
TemporaryFile' reveals that a temporary file is used:
To summarize, if you are able to specify the format of the stream
input and the coder does not require seek, then a temporary file will
usually be avoided. Use '-debug TemporaryFile' to learn when
temporary files are being used.
Ultimately, you may find it easiest to simply redirect (MAGICK_TMPDIR
environment variable) the temporary file location that GraphicsMagick
uses to a RAM-backed temporary file directory.
Hi,
is there a way that I can force GM not to generate any temporary files at all?
My goal is to pipe image files to and from GM (via stdio) as fast as possible without putting load onto the hard drive.
Thanks in advance
On Mon, 14 Apr 2014, KnownIdentifier wrote:
Temporary files are used for several purposes. For huge images where
the decoded representation can't fit entirely in memory, disk files
are used to support the "pixel cache". When external programs are
used (e.g. Ghostscript) these programs may require use of temporary
files to pass input data and obtain output data. When input is piped
from stdio then if the coder (reader) for the input format is declared
to need to be able to seek in the input stream (MagickInfo
seekable_stream is set to True), then it is necessary to buffer the
input from stdio to a temporary file since pipes do not support
seek().
For some formats (e.g. TIFF), using seek is unavoidable. For some
other formats, seek was used due to the programmer being lazy or due
to some notion of efficiency (skip over rather than read).
These formats are currently declared as requiring seek:
BMP, CALS, CUT, DCM, FITS, FPX, ICON, JP2, MAC, MAT, META, MIFF, MVG,
PALM, PCD, PCX, PDF, PICT, PNG, PS2, PS3, RLA, SGI, TIFF, TOPOL, TXT,
WMF, WPG, and XCF.
In order to support automatic file type identification (in case it is
not already specified), GraphicsMagick reads the first part of the
file data to determine the file format and then rewinds the file
descriptor to the beginning of the file before invoking the correct
decoder. It is not possible to rewind the file descriptor on a pipe.
It is possible to buffer that input for subsequent re-use but this has
not yet been implemented. For these cases, explicitly specifying the
file format will avoid use of a temporary file:
For example, without specifying the input format, '-debug
TemporaryFile' reveals that a temporary file is used:
but if we specify the format of the input file, then there is no more
use of a temporary file:
% cat Sunrise.jpg | gm convert -debug TemporaryFile jpeg:- null:To summarize, if you are able to specify the format of the stream
input and the coder does not require seek, then a temporary file will
usually be avoided. Use '-debug TemporaryFile' to learn when
temporary files are being used.
Ultimately, you may find it easiest to simply redirect (MAGICK_TMPDIR
environment variable) the temporary file location that GraphicsMagick
uses to a RAM-backed temporary file directory.
Bob
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/