=head1 NAME Imager::Filters - Entire Image Filtering Operations =head1 SYNOPSIS use Imager; $img = ...; $img->filter(type=>'autolevels'); $img->filter(type=>'autolevels', lsat=>0.2); $img->filter(type=>'turbnoise') # and lots others load_plugin("dynfilt/dyntest.so") or die "unable to load plugin\n"; $img->filter(type=>'lin_stretch', a=>35, b=>200); unload_plugin("dynfilt/dyntest.so") or die "unable to load plugin\n"; $out = $img->difference(other=>$other_img); =head1 DESCRIPTION Filters are operations that have similar calling interface. =head2 Types of Filters Here is a list of the filters that are always avaliable in Imager. This list can be obtained by running the C script that comes with the module source. Filter Arguments Default value autolevels lsat 0.1 usat 0.1 skew 0 bumpmap bump lightx lighty elevation 0 st 2 bumpmap_complex bump channel 0 tx 0 ty 0 Lx 0.2 Ly 0.4 Lz -1 cd 1.0 cs 40.0 n 1.3 Ia (0 0 0) Il (255 255 255) Is (255 255 255) contrast intensity conv coef fountain xa ya xb yb ftype linear repeat none combine none super_sample none ssample_param 4 segments(see below) gaussian stddev gradgen xo yo colors dist hardinvert mosaic size 20 noise amount 3 subtype 0 postlevels levels 10 radnoise xo 100 yo 100 ascale 17.0 rscale 0.02 turbnoise xo 0.0 yo 0.0 scale 10.0 unsharpmask stddev 2.0 scale 1.0 watermark wmark pixdiff 10 tx 0 ty 0 All parameters must have some value but if a parameter has a default value it may be omitted when calling the filter function. A reference of the filters follows: =over =item autolevels scales the value of each channel so that the values in the image will cover the whole possible range for the channel. I and I truncate the range by the specified fraction at the top and bottom of the range respectivly. =item bumpmap uses the channel I image I as a bumpmap on your image, with the light at (I, I), with a shadow length of I. =item bumpmap_complex uses the channel I image I as a bumpmap on your image. If Lz<0 the three L parameters are considered to be the direction of the light. If Lz>0 the L parameters are considered to be the light position. I is the ambient colour, I is the light colour, I is the color of specular highlights. I is the diffuse coefficient and I is the specular coefficient. I is the shininess of the surface. =item contrast scales each channel by I. Values of I < 1.0 will reduce the contrast. =item conv performs 2 1-dimensional convolutions on the image using the values from I. I should be have an odd length. =item fountain renders a fountain fill, similar to the gradient tool in most paint software. The default fill is a linear fill from opaque black to opaque white. The points A(xa, ya) and B(xb, yb) control the way the fill is performed, depending on the ftype parameter: =over =item linear the fill ramps from A through to B. =item bilinear the fill ramps in both directions from A, where AB defines the length of the gradient. =item radial A is the center of a circle, and B is a point on it's circumference. The fill ramps from the center out to the circumference. =item radial_square A is the center of a square and B is the center of one of it's sides. This can be used to rotate the square. The fill ramps out to the edges of the square. =item revolution A is the centre of a circle and B is a point on it's circumference. B marks the 0 and 360 point on the circle, with the fill ramping clockwise. =item conical A is the center of a circle and B is a point on it's circumference. B marks the 0 and point on the circle, with the fill ramping in both directions to meet opposite. =back The I option controls how the fill is repeated for some Is after it leaves the AB range: =over =item none no repeats, points outside of each range are treated as if they were on the extreme end of that range. =item sawtooth the fill simply repeats in the positive direction =item triangle the fill repeats in reverse and then forward and so on, in the positive direction =item saw_both the fill repeats in both the positive and negative directions (only meaningful for a linear fill). =item tri_both as for triangle, but in the negative direction too (only meaningful for a linear fill). =back By default the fill simply overwrites the whole image (unless you have parts of the range 0 through 1 that aren't covered by a segment), if any segments of your fill have any transparency, you can set the I option to 'normal' to have the fill combined with the existing pixels. See the description of I in L. If your fill has sharp edges, for example between steps if you use repeat set to 'triangle', you may see some aliased or ragged edges. You can enable super-sampling which will take extra samples within the pixel in an attempt anti-alias the fill. The possible values for the super_sample option are: =over =item none no super-sampling is done =item grid a square grid of points are sampled. The number of points sampled is the square of ceil(0.5 + sqrt(ssample_param)). =item random a random set of points within the pixel are sampled. This looks pretty bad for low ssample_param values. =item circle the points on the radius of a circle within the pixel are sampled. This seems to produce the best results, but is fairly slow (for now). =back You can control the level of sampling by setting the ssample_param option. This is roughly the number of points sampled, but depends on the type of sampling. The segments option is an arrayref of segments. You really should use the Imager::Fountain class to build your fountain fill. Each segment is an array ref containing: =over =item start a floating point number between 0 and 1, the start of the range of fill parameters covered by this segment. =item middle a floating point number between start and end which can be used to push the color range towards one end of the segment. =item end a floating point number between 0 and 1, the end of the range of fill parameters covered by this segment. This should be greater than start. =item c0 =item c1 The colors at each end of the segment. These can be either Imager::Color or Imager::Color::Float objects. =item segment type The type of segment, this controls the way the fill parameter varies over the segment. 0 for linear, 1 for curved (unimplemented), 2 for sine, 3 for sphere increasing, 4 for sphere decreasing. =item color type The way the color varies within the segment, 0 for simple RGB, 1 for hue increasing and 2 for hue decreasing. =back Don't forget to use Imager::Fountain instead of building your own. Really. It even loads GIMP gradient files. =item gaussian performs a gaussian blur of the image, using I as the standard deviation of the curve used to combine pixels, larger values give bigger blurs. For a definition of Gaussian Blur, see: http://www.maths.abdn.ac.uk/~igc/tch/mx4002/notes/node99.html =item gradgen renders a gradient, with the given I at the corresponding points (x,y) in I and I. You can specify the way distance is measured for color blendeing by setting I to 0 for Euclidean, 1 for Euclidean squared, and 2 for Manhattan distance. =item hardinvert inverts the image, black to white, white to black. All channels are inverted, including the alpha channel if any. =item mosaic produces averaged tiles of the given I. =item noise adds noise of the given I to the image. If I is zero, the noise is even to each channel, otherwise noise is added to each channel independently. =item radnoise renders radiant Perlin turbulent noise. The centre of the noise is at (I, I), I controls the angular scale of the noise , and I the radial scale, higher numbers give more detail. =item postlevels alters the image to have only I distinct level in each channel. =item turbnoise renders Perlin turbulent noise. (I, I) controls the origin of the noise, and I the scale of the noise, with lower numbers giving more detail. =item unsharpmask performs an unsharp mask on the image. This is the result of subtracting a gaussian blurred version of the image from the original. I controls the stddev parameter of the gaussian blur. Each output pixel is: in + I * (in - blurred). =item watermark applies I as a watermark on the image with strength I, with an origin at (I, I) =back A demonstration of most of the filters can be found at: http://www.develop-help.com/imager/filters.html (This is a slow link.) =head2 Plugins It is possible to add filters to the module without recompiling the module itself. This is done by using DSOs (Dynamic shared object) avaliable on most systems. This way you can maintain our own filters and not have to get me to add it, or worse patch every new version of the Module. Modules can be loaded AND UNLOADED at runtime. This means that you can have a server/daemon thingy that can do something like: load_plugin("dynfilt/dyntest.so") or die "unable to load plugin\n"; $img->filter(type=>'lin_stretch', a=>35, b=>200); unload_plugin("dynfilt/dyntest.so") or die "unable to load plugin\n"; Someone decides that the filter is not working as it should - dyntest.c modified and recompiled. load_plugin("dynfilt/dyntest.so") or die "unable to load plugin\n"; $img->filter(%hsh); An example plugin comes with the module - Please send feedback to addi@umich.edu if you test this. Note: This seems to test ok on the following systems: Linux, Solaris, HPUX, OpenBSD, FreeBSD, TRU64/OSF1, AIX. If you test this on other systems please let me know. =head2 Image Difference You can create a new image that is the difference between 2 other images. my $diff = $img->difference(other=>$other_img); For each pixel in $img that is different to the pixel in $other_img, the pixel from $other_img is given, otherwise the pixel is transparent black. This can be used for debugging image differences ("Where are they different?"), and for optimizing animated GIFs. Note that $img and $other_img must have the same number of channels. The width and heigh of $diff will be the minimum of each of the width and height of $img and $other_img. =cut