NAME

  tifffastcrop - extracts (crops) a rectangular region from a tiff 
file, avoiding loading the full source image input.tif into memory.

USAGE

  tifffastcrop [options] -E x,y,w,l input.tif [output]

DESCRIPTION

tifffastcrop takes a single-image TIFF file, reads the rectangular region of width w, length l, and top left corner at position (x,y) in pixels and stores it into a new file. The function is similar to what tiffcrop from LibTIFF does but tifffastcrop works also on very large TIFF files and it tries to read as little as possible from the source image into memory, whereas many programs open the whole image even if a very small region is requested. Therefore, it is much faster on large files.

If the "output" name is provided, the result is stored into a file with that name, in the format guessed from the extension of this filename if guess is possible (and in TIFF format if not), or in the format specified by options. Otherwise, the name given to the output file is created by adding the specification of the cropped region after the name of the original image and before the extension.

PERFORMANCES

In principle, cropping a (small) region from a large TIFF file can also be achieved with several tools, as tiffcrop, ImageMagick and GraphicsMagick. However, most of the programs start with opening and deciphering the whole image either in memory or in a huge temporary file on the disk, which makes them quite slow, and often unable to complete the task by lack of memory.

In contrast, tifffastcrop reads as little as possible from the source image. If the input file is a tiled TIFF with reasonable tile size, it should read barely more than the cropped region. This yields speedup and guarantees successful termination of the process even on computers with modest memory. Eg. to crop a region of size 256x256 pixels in the middle of a JPEG-compressed tiled TIFF image of size 180224x70144, on a computer with 16 GiB of RAM and an i7 CPU, tifffastcrop needs 0.3 seconds while GraphicsMagick needs more than 80 minutes and tiffcrop and ImageMagick fail.

OPTIONS

-v

Verbose monitoring.

-T

Do not report TIFF errors or warnings. Under Windows, they are reported with noisy dialog boxes.

-E <x in pixels>,<y in pixels>,<width in pixels>,<length in pixels>

Specification of the rectangular region to extract (crop). The top left corner (x,y) has to be inside the source image. Special value -1 for width or length means "as big as possible". If the rectangle extends beyond the limits of the source image, its dimensions are adjusted. Examples: -E 10,20,512,256 or -E 0,0,-1,-1 (the latter means full image, whatever its dimensions).

-o <offset in bytes>

Specify that only image in TIFF directory at position offset in source file will be read and handled. Takes precedence over -d option.

-d <range 1>[,<range 2>...]

Specify non-empty ranges of TIFF directory numbers (starting at 0) from which extracts should be made. A range is specified as <starting number>-<ending number> or <starting number>:<ending number>. Ending number is included: for instance, range 3-3 means fourth directory. If starting number is omitted, is it assumed to be 0 (first directory). If ending number is omitted or -1, it means the last directory of the file.

If several -d options are given, their ranges cumulate.

-j[#]

Requests output of JPEG files rather than the default TIFF. Optional number # in the range 0 to 100 indicates wanted JPEG quality (default is 75).

-p[#]

Requests output of PNG files rather than the default TIFF. Optional number # in the range 0 to 9 indicates wanted PNG compression level (default is currently 6).

If several of -j, -p, and -c options are given, only the last one takes effect.

-c <method>[:opt[:opt]...]

Requests output of TIFF files compressed with method. Method can be `none' for no compression, `jpeg', `lzw', `zip'... as provided by the LibTIFF library (see libtiff (3TIFF)). By default, the same compression as in the input TIFF file is used.

Method-specific details of the wished compression can be specified by adding one or several group of characters starting with a colon `:' after the methods's name, as follows.

Option to (TIFF compressed with) JPEG method: :# set compression quality level as in option -j (see above).

LZW, Deflate (zip) and LZMA2 options: :# set predictor value :p# set compression level.

For example, -c lzw:2 to get LZW-encoded data with horizontal differencing, -c zip:3:p9 for Deflate encoding with maximum compression level and floating point predictor, -c jpeg:r:50 for JPEG-encoded RGB data at quality 50%.