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diff --git a/libjpegtwrp/jpegtran.1 b/libjpegtwrp/jpegtran.1 deleted file mode 100644 index 6de18e2af..000000000 --- a/libjpegtwrp/jpegtran.1 +++ /dev/null @@ -1,238 +0,0 @@ -.TH JPEGTRAN 1 "3 August 1997" -.SH NAME -jpegtran \- lossless transformation of JPEG files -.SH SYNOPSIS -.B jpegtran -[ -.I options -] -[ -.I filename -] -.LP -.SH DESCRIPTION -.LP -.B jpegtran -performs various useful transformations of JPEG files. -It can translate the coded representation from one variant of JPEG to another, -for example from baseline JPEG to progressive JPEG or vice versa. It can also -perform some rearrangements of the image data, for example turning an image -from landscape to portrait format by rotation. -.PP -.B jpegtran -works by rearranging the compressed data (DCT coefficients), without -ever fully decoding the image. Therefore, its transformations are lossless: -there is no image degradation at all, which would not be true if you used -.B djpeg -followed by -.B cjpeg -to accomplish the same conversion. But by the same token, -.B jpegtran -cannot perform lossy operations such as changing the image quality. -.PP -.B jpegtran -reads the named JPEG/JFIF file, or the standard input if no file is -named, and produces a JPEG/JFIF file on the standard output. -.SH OPTIONS -All switch names may be abbreviated; for example, -.B \-optimize -may be written -.B \-opt -or -.BR \-o . -Upper and lower case are equivalent. -British spellings are also accepted (e.g., -.BR \-optimise ), -though for brevity these are not mentioned below. -.PP -To specify the coded JPEG representation used in the output file, -.B jpegtran -accepts a subset of the switches recognized by -.BR cjpeg : -.TP -.B \-optimize -Perform optimization of entropy encoding parameters. -.TP -.B \-progressive -Create progressive JPEG file. -.TP -.BI \-restart " N" -Emit a JPEG restart marker every N MCU rows, or every N MCU blocks if "B" is -attached to the number. -.TP -.BI \-scans " file" -Use the scan script given in the specified text file. -.PP -See -.BR cjpeg (1) -for more details about these switches. -If you specify none of these switches, you get a plain baseline-JPEG output -file. The quality setting and so forth are determined by the input file. -.PP -The image can be losslessly transformed by giving one of these switches: -.TP -.B \-flip horizontal -Mirror image horizontally (left-right). -.TP -.B \-flip vertical -Mirror image vertically (top-bottom). -.TP -.B \-rotate 90 -Rotate image 90 degrees clockwise. -.TP -.B \-rotate 180 -Rotate image 180 degrees. -.TP -.B \-rotate 270 -Rotate image 270 degrees clockwise (or 90 ccw). -.TP -.B \-transpose -Transpose image (across UL-to-LR axis). -.TP -.B \-transverse -Transverse transpose (across UR-to-LL axis). -.PP -The transpose transformation has no restrictions regarding image dimensions. -The other transformations operate rather oddly if the image dimensions are not -a multiple of the iMCU size (usually 8 or 16 pixels), because they can only -transform complete blocks of DCT coefficient data in the desired way. -.PP -.BR jpegtran 's -default behavior when transforming an odd-size image is designed -to preserve exact reversibility and mathematical consistency of the -transformation set. As stated, transpose is able to flip the entire image -area. Horizontal mirroring leaves any partial iMCU column at the right edge -untouched, but is able to flip all rows of the image. Similarly, vertical -mirroring leaves any partial iMCU row at the bottom edge untouched, but is -able to flip all columns. The other transforms can be built up as sequences -of transpose and flip operations; for consistency, their actions on edge -pixels are defined to be the same as the end result of the corresponding -transpose-and-flip sequence. -.PP -For practical use, you may prefer to discard any untransformable edge pixels -rather than having a strange-looking strip along the right and/or bottom edges -of a transformed image. To do this, add the -.B \-trim -switch: -.TP -.B \-trim -Drop non-transformable edge blocks. -.PP -Obviously, a transformation with -.B \-trim -is not reversible, so strictly speaking -.B jpegtran -with this switch is not lossless. Also, the expected mathematical -equivalences between the transformations no longer hold. For example, -.B \-rot 270 -trim -trims only the bottom edge, but -.B \-rot 90 -trim -followed by -.B \-rot 180 -trim -trims both edges. -.PP -Another not-strictly-lossless transformation switch is: -.TP -.B \-grayscale -Force grayscale output. -.PP -This option discards the chrominance channels if the input image is YCbCr -(ie, a standard color JPEG), resulting in a grayscale JPEG file. The -luminance channel is preserved exactly, so this is a better method of reducing -to grayscale than decompression, conversion, and recompression. This switch -is particularly handy for fixing a monochrome picture that was mistakenly -encoded as a color JPEG. (In such a case, the space savings from getting rid -of the near-empty chroma channels won't be large; but the decoding time for -a grayscale JPEG is substantially less than that for a color JPEG.) -.PP -.B jpegtran -also recognizes these switches that control what to do with "extra" markers, -such as comment blocks: -.TP -.B \-copy none -Copy no extra markers from source file. This setting suppresses all -comments and other excess baggage present in the source file. -.TP -.B \-copy comments -Copy only comment markers. This setting copies comments from the source file, -but discards any other inessential data. -.TP -.B \-copy all -Copy all extra markers. This setting preserves miscellaneous markers -found in the source file, such as JFIF thumbnails and Photoshop settings. -In some files these extra markers can be sizable. -.PP -The default behavior is -.BR "\-copy comments" . -(Note: in IJG releases v6 and v6a, -.B jpegtran -always did the equivalent of -.BR "\-copy none" .) -.PP -Additional switches recognized by jpegtran are: -.TP -.BI \-maxmemory " N" -Set limit for amount of memory to use in processing large images. Value is -in thousands of bytes, or millions of bytes if "M" is attached to the -number. For example, -.B \-max 4m -selects 4000000 bytes. If more space is needed, temporary files will be used. -.TP -.BI \-outfile " name" -Send output image to the named file, not to standard output. -.TP -.B \-verbose -Enable debug printout. More -.BR \-v 's -give more output. Also, version information is printed at startup. -.TP -.B \-debug -Same as -.BR \-verbose . -.SH EXAMPLES -.LP -This example converts a baseline JPEG file to progressive form: -.IP -.B jpegtran \-progressive -.I foo.jpg -.B > -.I fooprog.jpg -.PP -This example rotates an image 90 degrees clockwise, discarding any -unrotatable edge pixels: -.IP -.B jpegtran \-rot 90 -trim -.I foo.jpg -.B > -.I foo90.jpg -.SH ENVIRONMENT -.TP -.B JPEGMEM -If this environment variable is set, its value is the default memory limit. -The value is specified as described for the -.B \-maxmemory -switch. -.B JPEGMEM -overrides the default value specified when the program was compiled, and -itself is overridden by an explicit -.BR \-maxmemory . -.SH SEE ALSO -.BR cjpeg (1), -.BR djpeg (1), -.BR rdjpgcom (1), -.BR wrjpgcom (1) -.br -Wallace, Gregory K. "The JPEG Still Picture Compression Standard", -Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44. -.SH AUTHOR -Independent JPEG Group -.SH BUGS -Arithmetic coding is not supported for legal reasons. -.PP -The transform options can't transform odd-size images perfectly. Use -.B \-trim -if you don't like the results without it. -.PP -The entire image is read into memory and then written out again, even in -cases where this isn't really necessary. Expect swapping on large images, -especially when using the more complex transform options. |