Subject: [21] What if I need more than 8-bit precision?
Baseline JPEG stores images with 8 bits per color sample, in other words
24 bits per pixel for RGB images, 8 bits/pixel for grayscale, 32 bits/pixelfor CMYK, etc.
There is an extension that stores 12 bits/sample for applications that need higher accuracy.
Medical images, for example, are often 12-bit grayscale. The 12-bit extension is not very widely supported,
however. One package that does support it is the free IJG source code (see part 2, item 15).
For lossless JPEG, the standard permits any data precision between 2 and 16 bits per sample,
but high-precision lossless JPEG is even less widely supported than high-precision lossy JPEG.
The Stanford PVRG codec (see part 2, item 15) reportedly supports up to 16 bits/sample for lossless JPEG.
struct jpeg_decompress_struct {
jpeg_common_fields; /* Fields shared with jpeg_compress_struct */
/* Source of compressed data */
struct jpeg_source_mgr * src;
/* Basic description of image --- filled in by jpeg_read_header(). */
/* Application may inspect these values to decide how to process image. */
JDIMENSION image_width; /* nominal image width (from SOF marker) */
JDIMENSION image_height; /* nominal image height */
int num_components; /* # of color components in JPEG image */
J_COLOR_SPACE jpeg_color_space; /* colorspace of JPEG image */
/* image_width는 폭 image_height는 높이 그리고 num_components는 몇개의 색상이 있는지를 알려준다. * jpeg는 각 element당 8bit씩을 사용하고, RGB는 각 8bit * 3 = 24bits * Grayscale은 8bit * 1(단일색상) = 8bits 이런식으로 color depth를 계산하면 된다. */
/* Decompression processing parameters --- these fields must be set before
* calling jpeg_start_decompress(). Note that jpeg_read_header() initializes
* them to default values.
*/
J_COLOR_SPACE out_color_space; /* colorspace for output */ /* 윈도우에서 색대표라고 나오는 것이다. 출력시의 색상계를 의미함 */
unsigned int scale_num, scale_denom; /* fraction by which to scale image */
double output_gamma; /* image gamma wanted in output */
boolean quantize_colors; /* TRUE=colormapped output wanted */
/* the following are ignored if not quantize_colors: */
J_DITHER_MODE dither_mode; /* type of color dithering to use */
boolean two_pass_quantize; /* TRUE=use two-pass color quantization */
int desired_number_of_colors; /* max # colors to use in created colormap */
/* these are significant only in buffered-image mode: */
boolean enable_1pass_quant; /* enable future use of 1-pass quantizer */
boolean enable_external_quant;/* enable future use of external colormap */
boolean enable_2pass_quant; /* enable future use of 2-pass quantizer */
/* Description of actual output image that will be returned to application.
* These fields are computed by jpeg_start_decompress().
* You can also use jpeg_calc_output_dimensions() to determine these values
* in advance of calling jpeg_start_decompress().
*/
JDIMENSION output_width; /* scaled image width */
JDIMENSION output_height; /* scaled image height */
int out_color_components; /* # of color components in out_color_space */
int output_components; /* # of color components returned */
/* output_components is 1 (a colormap index) when quantizing colors;
* otherwise it equals out_color_components.
*/
int rec_outbuf_height; /* min recommended height of scanline buffer */
/* If the buffer passed to jpeg_read_scanlines() is less than this many rows
* high, space and time will be wasted due to unnecessary data copying.
* Usually rec_outbuf_height will be 1 or 2, at most 4.
*/
/* When quantizing colors, the output colormap is described by these fields.
* The application can supply a colormap by setting colormap non-NULL before
* calling jpeg_start_decompress; otherwise a colormap is created during
* jpeg_start_decompress or jpeg_start_output.
* The map has out_color_components rows and actual_number_of_colors columns.
*/
int actual_number_of_colors; /* number of entries in use */
JSAMPARRAY colormap; /* The color map as a 2-D pixel array */
/* State variables: these variables indicate the progress of decompression.
* The application may examine these but must not modify them.
*/
/* Row index of next scanline to be read from jpeg_read_scanlines().
* Application may use this to control its processing loop, e.g.,
* "while (output_scanline < output_height)".
*/
JDIMENSION output_scanline; /* 0 .. output_height-1 */
/* Current input scan number and number of iMCU rows completed in scan.
* These indicate the progress of the decompressor input side.
*/
int input_scan_number; /* Number of SOS markers seen so far */
JDIMENSION input_iMCU_row; /* Number of iMCU rows completed */
/* The "output scan number" is the notional scan being displayed by the
* output side. The decompressor will not allow output scan/row number
* to get ahead of input scan/row, but it can fall arbitrarily far behind.
*/
int output_scan_number; /* Nominal scan number being displayed */
JDIMENSION output_iMCU_row; /* Number of iMCU rows read */
/* Current progression status. coef_bits[c][i] indicates the precision
* with which component c's DCT coefficient i (in zigzag order) is known.
* It is -1 when no data has yet been received, otherwise it is the point
* transform (shift) value for the most recent scan of the coefficient
* (thus, 0 at completion of the progression).
* This pointer is NULL when reading a non-progressive file.
*/
int (*coef_bits)[DCTSIZE2]; /* -1 or current Al value for each coef */
/* Internal JPEG parameters --- the application usually need not look at
* these fields. Note that the decompressor output side may not use
* any parameters that can change between scans.
*/
/* Quantization and Huffman tables are carried forward across input
* datastreams when processing abbreviated JPEG datastreams.
*/
JQUANT_TBL * quant_tbl_ptrs[NUM_QUANT_TBLS];
/* ptrs to coefficient quantization tables, or NULL if not defined */
JHUFF_TBL * dc_huff_tbl_ptrs[NUM_HUFF_TBLS];
JHUFF_TBL * ac_huff_tbl_ptrs[NUM_HUFF_TBLS];
/* ptrs to Huffman coding tables, or NULL if not defined */
/* These parameters are never carried across datastreams, since they
* are given in SOF/SOS markers or defined to be reset by SOI.
*/
int data_precision; /* bits of precision in image data */
jpeg_component_info * comp_info;
/* comp_info[i] describes component that appears i'th in SOF */
UINT8 arith_dc_L[NUM_ARITH_TBLS]; /* L values for DC arith-coding tables */
UINT8 arith_dc_U[NUM_ARITH_TBLS]; /* U values for DC arith-coding tables */
UINT8 arith_ac_K[NUM_ARITH_TBLS]; /* Kx values for AC arith-coding tables */
unsigned int restart_interval; /* MCUs per restart interval, or 0 for no restart */
/* These fields record data obtained from optional markers recognized by
* the JPEG library.
*/
boolean saw_JFIF_marker; /* TRUE iff a JFIF APP0 marker was found */
/* Data copied from JFIF marker; only valid if saw_JFIF_marker is TRUE: */
UINT8 JFIF_major_version; /* JFIF version number */
UINT8 JFIF_minor_version;
UINT8 density_unit; /* JFIF code for pixel size units */
UINT16 X_density; /* Horizontal pixel density */
UINT16 Y_density; /* Vertical pixel density */
boolean saw_Adobe_marker; /* TRUE iff an Adobe APP14 marker was found */
UINT8 Adobe_transform; /* Color transform code from Adobe marker */ /* X_density, Y_density는 DPI 단위의 수평,수직 해상도를 나타낸다. */
boolean CCIR601_sampling; /* TRUE=first samples are cosited */
/* Aside from the specific data retained from APPn markers known to the
* library, the uninterpreted contents of any or all APPn and COM markers
* can be saved in a list for examination by the application.
*/
jpeg_saved_marker_ptr marker_list; /* Head of list of saved markers */
/* Remaining fields are known throughout decompressor, but generally
* should not be touched by a surrounding application.
*/
/*
* These fields are computed during decompression startup
*/
int max_h_samp_factor; /* largest h_samp_factor */
int max_v_samp_factor; /* largest v_samp_factor */
int min_DCT_scaled_size; /* smallest DCT_scaled_size of any component */
JDIMENSION total_iMCU_rows; /* # of iMCU rows in image */
/* The coefficient controller's input and output progress is measured in
* units of "iMCU" (interleaved MCU) rows. These are the same as MCU rows
* in fully interleaved JPEG scans, but are used whether the scan is
* interleaved or not. We define an iMCU row as v_samp_factor DCT block
* rows of each component. Therefore, the IDCT output contains
* v_samp_factor*DCT_scaled_size sample rows of a component per iMCU row.
*/
JSAMPLE * sample_range_limit; /* table for fast range-limiting */
/*
* These fields are valid during any one scan.
* They describe the components and MCUs actually appearing in the scan.
* Note that the decompressor output side must not use these fields.
*/
int comps_in_scan; /* # of JPEG components in this scan */
jpeg_component_info * cur_comp_info[MAX_COMPS_IN_SCAN];
/* *cur_comp_info[i] describes component that appears i'th in SOS */
JDIMENSION MCUs_per_row; /* # of MCUs across the image */
JDIMENSION MCU_rows_in_scan; /* # of MCU rows in the image */
int blocks_in_MCU; /* # of DCT blocks per MCU */
int MCU_membership[D_MAX_BLOCKS_IN_MCU];
/* MCU_membership[i] is index in cur_comp_info of component owning */
/* i'th block in an MCU */
int Ss, Se, Ah, Al; /* progressive JPEG parameters for scan */
/* This field is shared between entropy decoder and marker parser.
* It is either zero or the code of a JPEG marker that has been
* read from the data source, but has not yet been processed.
*/
int unread_marker;
u-boot에서 리눅스 커널로 bootargs를 넘겨주어 nfs를 연결할 경우, 기본값이면 UDP로 연결되게 된다.
mount로 확인해보면
# mount
rootfs on / type rootfs (rw)
/dev/root on / type nfs (rw,noatime,vers=2,rsize=4096,wsize=4096,hard,nolock,proto=tcp,timeo=600,retrans=2,addr=192.168.10.10)
proc on /proc type proc (rw)
/dev/sda1 on /root/sda1 type vfat (rw,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1)
Recommended Repository Layout
While Subversion's flexibility allows you to lay out your repository in any way that you choose, we recommend that you create a trunk directory to hold the “main line” of development, a branches directory to contain branch copies,
and a tags directory to contain tag copies. For example:
$ svn list file:///var/svn/repos
/trunk
/branches
/tags
You'll learn more about tags and branches in Chapter 4, Branching and Merging. For details and how to set up multiple projects, see the section called “Repository Layout” and the section called “Planning Your Repository Organization” to read more about project roots.
You'll need the following build tools to compile Subversion:
* autoconf 2.58 or later (Unix only)
* libtool 1.4 or later (Unix only)
* a reasonable C compiler (gcc, Visual Studio, etc.)
Subversion also depends on the following third-party libraries:
* libapr and libapr-util (REQUIRED for client and server)
The Apache Portable Runtime (APR) library provides an
abstraction of operating-system level services such as file
and network I/O, memory management, and so on. It also
provides convenience routines for things like hashtables,
checksums, and argument processing. While it was originally
developed for the Apache HTTP server, APR is a standalone
library used by Subversion and other products. It is a
critical dependency for all of Subversion; it's the layer
that allows Subversion clients and servers to run on
different operating systems.
* SQLite (REQUIRED for client and server)
Subversion uses SQLite to manage some internal databases.
* libz (REQUIRED for client and server)
Subversion uses zlib for compressing binary differences.
These diff streams are used everywhere -- over the network,
in the repository, and in the client's working copy.
* libserf (OPTIONAL for client)
The Serf libraries both allow the Subversion client
to send HTTP requests. This is necessary if you want your
client to access a repository served by the Apache HTTP
server. There is an alternate 'svnserve' server as well,
though, and clients automatically know how to speak the
svnserve protocol. Thus it's not strictly necessary for your
client to be able to speak HTTP... though we still recommend
that your client be built to speak both HTTP and svnserve
protocols.
* OpenSSL (OPTIONAL for client and server)
OpenSSL enables your client to access SSL-encrypted https://
URLs (using libserf) in addition to unencrypted http:// URLs.
To use SSL with Subversion's WebDAV server, Apache needs to
be compiled with OpenSSL as well.
* Berkeley DB (OPTIONAL for client and server)
There are two different repository 'back-end'
implementations. One implementation stores data in a flat
filesystem (known as FSFS); the other implementation stores
data in a Berkeley DB database (known as BDB). When you
create a repository, you have the option of specifying a
storage back-end. The Berkeley DB back-end will only be
available if the BDB libraries are discovered at compile
time.
* libsasl (OPTIONAL for client and server)
If the Cyrus SASL library is detected at compile time, then
the svn client (and svnserve server) will be able to utilize
SASL to do various forms of authentication when speaking the
svnserve protocol.
* Python, Perl, Java, Ruby (OPTIONAL)
Subversion is mostly a collection of C libraries with
well-defined APIs, with a small collection of programs that
use the APIs. If you want to build Subversion API bindings
for other languages, you need to have those languages
available at build time.
* KDELibs, GNOME Keyring (OPTIONAL for client)
Subversion contains optional support for storing passwords in
KWallet (KDE 4) or GNOME Keyring.
To create a new Subversion repository by converting an existing CVS repository, run the script like this: $ cvs2svn --svnrepos NEW_SVNREPOS CVSREPOS
To create a new Subversion repository containing only trunk commits,
and omitting all branches and tags from the CVS repository, do
$ cvs2svn --trunk-only --svnrepos NEW_SVNREPOS CVSREPOS
To create a Subversion dumpfile (suitable for 'svnadmin load') from a CVS repository, run it like this:
$ cvs2svn --dumpfile DUMPFILE CVSREPOS
To use an options file to define all of the conversion parameters, specify --options:
$ cvs2svn --options OPTIONSFILE
As it works, cvs2svn will create many temporary files in a temporary
directory called "cvs2svn-tmp" (or the directory specified with
--tmpdir). This is normal. If the entire conversion is successful,
however, those tempfiles will be automatically removed. If the
conversion is not successful, or if you specify the '--skip-cleanup'
option, cvs2svn will leave the temporary files behind for possible
debugging.
cvs2svn은 cvs 리파지터리를 svn으로 변환해주는 툴이다.
변환과정중에 하나라도 잘못된 ,v 파일(cvs의 history 파일)이 있으면 중지되고,
한글을 사용했을 경우, encoding 문제로 인해서 pass 2에서 문제가 발생한다.
ERROR: There were warnings converting author names and/or log messages
to unicode (see messages above). Please restart this pass
with one or more '--encoding' parameters or with '--fallback-encoding'.
$ man cvs2svn --encoding=encoding
Use encoding as the encoding for filenames, log messages, and
author names in the CVS repos. This option may be specified mul-
tiple times, in which case the encodings are tried in order until
one succeeds. Default: ascii. See
http://docs.python.org/lib/standard-encodings.html for a list of
other standard encodings.
--fallback-encoding=encoding
If none of the encodings specified with --encoding succeed in
decoding an author name or log message, then fall back to using
encoding in lossy 'replace' mode. Use of this option may cause
information to be lost, but at least it allows the conversion to
run to completion. This option only affects the encoding of log
messages and author names; there is no fallback encoding for
filenames. (By using an --options file, it is possible to spec-
ify a fallback encoding for filenames.) Default: disabled.
### Section for configuring tunnel agents.
[tunnels]
### Configure svn protocol tunnel schemes here. By default, only
### the 'ssh' scheme is defined. You can define other schemes to
### be used with 'svn+scheme://hostname/path' URLs. A scheme
### definition is simply a command, optionally prefixed by an
### environment variable name which can override the command if it
### is defined. The command (or environment variable) may contain
### arguments, using standard shell quoting for arguments with
### spaces. The command will be invoked as:
### <command> <hostname> svnserve -t
### (If the URL includes a username, then the hostname will be
### passed to the tunnel agent as <user>@<hostname>.) Here we
### redefine the built-in 'ssh' scheme to avoid an unfortunate
### interaction with the "ControlMaster auto" feature (for
### details, see Debian Bug #413102): ssh = $SVN_SSH ssh -o ControlMaster=no
### If you wanted to define a new 'rsh' scheme, to be used with
### 'svn+rsh:' URLs, you could do so as follows:
# rsh = rsh
### Or, if you wanted to specify a full path and arguments:
# rsh = /path/to/rsh -l myusername
### On Windows, if you are specifying a full path to a command,
### use a forward slash (/) or a paired backslash (\\) as the
### path separator. A single backslash will be treated as an
### escape for the following character.
DESCRIPTION
sftp is an interactive file transfer program, similar to ftp(1), which
performs all operations over an encrypted ssh(1) transport. It may also
use many features of ssh, such as public key authentication and compres-
sion. sftp connects and logs into the specified host, then enters an
interactive command mode.
The second usage format will retrieve files automatically if a non-inter-
active authentication method is used; otherwise it will do so after suc-
cessful interactive authentication.
The third usage format allows sftp to start in a remote directory.
The final usage format allows for automated sessions using the -b option.
In such cases, it is necessary to configure non-interactive authentica-
tion to obviate the need to enter a password at connection time (see
sshd(8) and ssh-keygen(1) for details). The options are as follows:
-1 Specify the use of protocol version 1.
-B buffer_size
Specify the size of the buffer that sftp uses when transferring
files. Larger buffers require fewer round trips at the cost of
higher memory consumption. The default is 32768 bytes.
-b batchfile
Batch mode reads a series of commands from an input batchfile
instead of stdin. Since it lacks user interaction it should be
used in conjunction with non-interactive authentication. A
batchfile of '-' may be used to indicate standard input. sftp
will abort if any of the following commands fail: get, put,
rename, ln, rm, mkdir, chdir, ls, lchdir, chmod, chown, chgrp,
lpwd, df, and lmkdir. Termination on error can be suppressed on
a command by command basis by prefixing the command with a '-'
character (for example, -rm /tmp/blah*).
-C Enables compression (via ssh's -C flag).
-F ssh_config
Specifies an alternative per-user configuration file for ssh(1).
This option is directly passed to ssh(1).
-o ssh_option
Can be used to pass options to ssh in the format used in
ssh_config(5). This is useful for specifying options for which
there is no separate sftp command-line flag. For example, to
specify an alternate port use: sftp -oPort=24. For full details
of the options listed below, and their possible values, see
ssh_config(5).
-P sftp_server_path
Connect directly to a local sftp server (rather than via ssh(1)).
This option may be useful in debugging the client and server.
-R num_requests
Specify how many requests may be outstanding at any one time.
Increasing this may slightly improve file transfer speed but will
increase memory usage. The default is 64 outstanding requests.
-S program
Name of the program to use for the encrypted connection. The
program must understand ssh(1) options.
-s subsystem | sftp_server
Specifies the SSH2 subsystem or the path for an sftp server on
the remote host. A path is useful for using sftp over protocol
version 1, or when the remote sshd(8) does not have an sftp sub-
system configured.
-v Raise logging level. This option is also passed to ssh.
INTERACTIVE COMMANDS
Once in interactive mode, sftp understands a set of commands similar to
those of ftp(1). Commands are case insensitive. Pathnames that contain
spaces must be enclosed in quotes. Any special characters contained
within pathnames that are recognized by glob(3) must be escaped with
backslashes ('\').
bye Quit sftp.
cd path
Change remote directory to path.
chgrp grp path
Change group of file path to grp. path may contain glob(3) char-
acters and may match multiple files. grp must be a numeric GID.
chmod mode path
Change permissions of file path to mode. path may contain
glob(3) characters and may match multiple files.
chown own path
Change owner of file path to own. path may contain glob(3) char-
acters and may match multiple files. own must be a numeric UID.
df [-hi] [path]
Display usage information for the filesystem holding the current
directory (or path if specified). If the -h flag is specified,
the capacity information will be displayed using "human-readable"
suffixes. The -i flag requests display of inode information in
addition to capacity information. This command is only supported
on servers that implement the ``statvfs@openssh.com'' extension.
exit Quit sftp.
get [-P] remote-path [local-path]
Retrieve the remote-path and store it on the local machine. If
the local path name is not specified, it is given the same name
it has on the remote machine. remote-path may contain glob(3)
characters and may match multiple files. If it does and
local-path is specified, then local-path must specify a direc-
tory. If the -P flag is specified, then full file permissions
and access times are copied too.
help Display help text.
lcd path
Change local directory to path.
lls [ls-options [path]]
Display local directory listing of either path or current direc-
tory if path is not specified. ls-options may contain any flags
supported by the local system's ls(1) command. path may contain
glob(3) characters and may match multiple files.
lmkdir path
Create local directory specified by path.
ln oldpath newpath
Create a symbolic link from oldpath to newpath.
lpwd Print local working directory.
ls [-1aflnrSt] [path]
Display a remote directory listing of either path or the current
directory if path is not specified. path may contain glob(3)
characters and may match multiple files.
The following flags are recognized and alter the behaviour of ls
accordingly:
-1 Produce single columnar output.
-a List files beginning with a dot ('.').
-f Do not sort the listing. The default sort order is lexi-
cographical.
-l Display additional details including permissions and own-
ership information.
-n Produce a long listing with user and group information
presented numerically.
-r Reverse the sort order of the listing.
-S Sort the listing by file size.
-t Sort the listing by last modification time.
lumask umask
Set local umask to umask.
mkdir path
Create remote directory specified by path.
progress
Toggle display of progress meter.
put [-P] local-path [remote-path]
Upload local-path and store it on the remote machine. If the
remote path name is not specified, it is given the same name it
has on the local machine. local-path may contain glob(3) charac-
ters and may match multiple files. If it does and remote-path is
specified, then remote-path must specify a directory. If the -P
flag is specified, then the file's full permission and access
time are copied too.
pwd Display remote working directory.
quit Quit sftp.
rename oldpath newpath
Rename remote file from oldpath to newpath.
rm path
Delete remote file specified by path.
rmdir path
Remove remote directory specified by path.
symlink oldpath newpath
Create a symbolic link from oldpath to newpath.
version
Display the sftp protocol version.
! command
Execute command in local shell.
! Escape to local shell.
? Synonym for help.
SEE ALSO
ftp(1), ls(1), scp(1), ssh(1), ssh-add(1), ssh-keygen(1), glob(3),
ssh_config(5), sftp-server(8), sshd(8)
T. Ylonen and S. Lehtinen, SSH File Transfer Protocol, draft-ietf-secsh-
filexfer-00.txt, January 2001, work in progress material.
