tiffdither¶
Synopsis¶
tiffdither [ options ] input.tif output.tif
Description¶
tiffdither converts a single channel 8-bit greyscale image to a bilevel image using Floyd-Steinberg error propagation with thresholding.
Options¶
- -c compress¶
Specify the compression to use for data written to the output file:
Compression
Description
none
no compression
packbits
PackBits compression
lzw
Lempel-Ziv & Welch compression
zip
Deflate compression
g3
CCITT Group 3 (T.4) compression
g4
for CCITT Group 4 (T.6) compression
By default tiffdither will compress data according to the value of the
Compressiontag found in the source file.The CCITT Group 3 and Group 4 compression algorithms can only be used with bilevel data.
Group 3 compression can be specified together with several T.4-specific options:
1dfor 1-dimensional encoding,2dfor 2-dimensional encoding, andfillto force each encoded scanline to be zero-filled so that the terminating EOL code lies on a byte boundary. Group 3-specific options are specified by appending a:-separated list to theg3option; e.g.-c g3:2d:fillto get 2D-encoded data with byte-aligned EOL codes.LZW compression can be specified together with a
predictorvalue. A predictor value of 2 causes each scanline of the output image to undergo horizontal differencing before it is encoded; a value of 1 forces each scanline to be encoded without differencing. LZW-specific options are specified by appending a:-separated list to thelzwoption; e.g.-c lzw:2for LZW compression with horizontal differencing.
- -f¶
Specify the bit fill order to use in writing output data. By default, tiffdither will create a new file with the same fill order as the original. Specifying -f lsb2msb will force data to be written with the
FillOrdertag set toLSB2MSB, while -f msb2lsb will force data to be written with theFillOrdertag set toMSB2LSB.
- -r¶
Make each strip have no more than the given number of rows.
- -t¶
Set the threshold value for dithering. By default the threshold value is 128.
Notes¶
The dither algorithm is taken from the tiffmedian program (written by Paul Heckbert).