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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2023-09-07 16:26:28 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2023-09-07 16:26:28 +0000 |
| commit | 851f8a113827e42ae618423fdab09cb0a67dc4e4 (patch) | |
| tree | c7975f26f69fa817d5de575a5c97d0a585b4e999 /pamaddnoise.html | |
| parent | 3195997e71a1ad9686da91a1d14cda2d81d3eb52 (diff) | |
| download | netpbm-mirror-851f8a113827e42ae618423fdab09cb0a67dc4e4.tar.gz netpbm-mirror-851f8a113827e42ae618423fdab09cb0a67dc4e4.tar.xz netpbm-mirror-851f8a113827e42ae618423fdab09cb0a67dc4e4.zip | |
miscellaneous update
git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@4637 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'pamaddnoise.html')
| -rw-r--r-- | pamaddnoise.html | 99 |
1 files changed, 68 insertions, 31 deletions
diff --git a/pamaddnoise.html b/pamaddnoise.html index 3a0f3903..0d1609bd 100644 --- a/pamaddnoise.html +++ b/pamaddnoise.html @@ -2,7 +2,7 @@ <html><head><title>Pamaddnoise User Manual</title></head> <body> <h1>pamaddnoise</h1> -Updated: 12 December 2020 +Updated: 21 August 2023 <br> <a href="#index">Table Of Contents</a> @@ -81,60 +81,97 @@ Common Options</a>), <b>pamaddnoise</b> recognizes the following command line options: <dl compact> -<dt><b>-lambda</b> <i>value</i> +<dt><b>-type</b> <i>noise_type</i> + +<dd> +Select type of noise by name. The following noise types are +available: gaussian, multiplicative_gaussian, impulse, laplacian, +poisson. Only enough letters to be unique are required for the noise +type option. The default noise type is <b>gaussian</b>. + +<dl> +<dt><b>gaussian</b> + <dd>To each sample value is added the value of a two Gaussian random variables. + The variance of one is independent of the sample value, while the variance + of the other is proportional to the sample value. You control these + variances with options <b>-sigma1</b> and <b>-sigma2</b> (and can eliminate + either by setting the variance to 0). The mean of the Gaussian + distributions is 0. + +<dt><b>multiplicative_gaussian</b> +<dt><b>impulse</b> + <dd>This is "salt and pepper" noise. Samples are changed randomly + to zero or full brightness or left alone. This is also know as salt and + pepper noise, as in a grayscale picture, it adds white pixels and black + pixels, which look like salt and pepper, respectively. Control this with + options <b>-tolerance</b> and <b>-salt</b>. + +<dt><b>laplacian</b> + +<dt><b>poisson</b> +</dl> -<dd>This is the expected value of the Poisson distribution for a sample value - of mximum intensity. The expected value for other intensities is - proportional; e.g. for half intensity, it is half this value. +<dt><b>-lambda</b> <i>value</i> -<p>This is meaningful only with <b>-type=poisson</b>. +<dd> +This is valid only with <b>-type=poisson</b>. It is the expected value +of the Poisson distribution for a sample value of mximum intensity. The +expected value for other intensities is proportional; e.g. for half intensity, +it is half this value. <p>The default value is 12. <dt><b>-lsigma</b> <i>value</i> -<dd>Used for laplacian noise only. The default value is 10.0. +<dd>This is menaingful only for laplacian noise. + +<p>The default value is 10.0. <dt><b>-mgsigma</b> <i>value</i> -<dd>Used for multiplicative gaussian noise only. The default value is -0.5. +<dd>This is valid only for multiplicative gaussian noise. + +<p>The default value is 0.5. <dt><b>-seed</b> <i>int</i> -<dd>Used for all noise types. Set the initial random number generator -seed value. +<dd>This is the random number generator seed value. Use this to get + repeatable results. <dt><b>-sigma1</b> <i>value</i> -<dd>Used for gaussian noise only. The default value is 4.0. +<dd>This is valid only for gaussian noise. It is the standard deviation + of the Gaussian random variable that is multiplied by the square root of + each sample value and added to that sample value. +<p> + The default value is 4.0. <dt><b>-sigma2</b> <i>value</i> -<dd>Used for gaussian noise only. The default value is 20.0. +<dd>This is valid only for gaussian noise. + It is the standard deviation of the Gaussian random variable that is + added directly to each sample value. +<p> +The default value is 20.0. -<dt><b>-tolerance</b> <i>ratio</i> +<dt><b>-tolerance</b> <i>fraction</i> -<dd> -Used for impulse noise only. The default value is 0.10. This means -that 5% of all pixel values will be set to 0 and 5% will be set to -the maxval +<dd>This is valid only for impulse noise. + <i>fraction</i> is the fraction of samples that are changed + in the output. Whether each is changed to salt or pepper is controlled by + <b>-salt</b>. -<dt><b>-type</b> <i>noise_type</i> +<p>The default value is 0.10. -<dd> -Select type of noise by name. The following noise types are -available: gaussian, multiplicative_gaussian, impulse, laplacian, -poisson. Only enough letters to be unique are required for the noise -type option. The default noise type is <b>gaussian</b>. +<dt><b>-salt=<i>fraction</i></b> + <dd>This is valid only for impulse noise. <i>fraction</i> is the + fraction of the pixels that are changed that are changed to salt (maxval); + the rest are changed to pepper (0). -<ul> -<li><b>gaussian</b> -<li><b>multiplicative_gaussian</b> -<li><b>impulse</b> -<li><b>laplacian</b> -<li><b>poisson</b> -</ul> +<p>The default is 0.5 (half salt, half pepper). + +<p>This option was new in Netpbm 11.04 (September 2023). Before that, the + noise is always half salt and half pepper. </dl> |