% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
-% AcquireResizeFilter() allocates the ResizeFilter structure. Choose
-% from these filters:
+% AcquireResizeFilter() allocates the ResizeFilter structure. Choose from
+% these filters:
%
% FIR (Finite impulse Response) Filters
% Box Triangle Quadratic
% settings for that filter from a internal table. However any provided
% 'expert' settings (see below) may override this selection.
%
-% FIR filters are used as is, and are limited to that filters support
-% window (unless over-ridden). 'Gaussian' while classed as an IIR
-% filter, is also simply clipped by its support size (currently 1.5
-% or approximatally 3*sigma as recommended by many references)
-%
-% The special a 'cylindrical' filter flag will promote the default
-% 4-lobed Windowed Sinc filter to a 3-lobed Windowed Jinc equivelent,
-% which is better suited to this style of image resampling. This
-% typically happens when using such a filter for images distortions.
-%
-% Directly requesting 'Sinc', 'Jinc' function as a filter will force
-% the use of function without any windowing, or promotion for
-% cylindrical usage. This is not recommended, except by image
-% processing experts, especially as part of expert option filter
-% function selection.
-%
-% Two forms of the 'Sinc' function are available: Sinc and SincFast.
-% Sinc is computed using the traditional sin(pi*x)/(pi*x); it is
-% selected if the user specifically specifies the use of a Sinc
-% filter. SincFast uses highly accurate (and fast) polynomial (low Q)
-% and rational (high Q) approximations, and will be used by default in
-% most cases.
-%
-% The Lanczos filter is a special 3-lobed Sinc-windowed Sinc filter
-% (promoted to Jinc-windowed Jinc for cylindrical (Elliptical
-% Weighted Average) use). The Sinc version is the most popular
-% windowed filter.
-%
-% LanczosSharp is a slightly sharpened (blur=0.9812505644269356 < 1)
-% form of the Lanczos filter, specifically designed for EWA
-% distortion (as a Jinc-Jinc); it can also be used as a slightly
-% sharper orthogonal Lanczos (Sinc-Sinc) filter. The chosen blur
-% value comes as close as possible to satisfying the following
-% condition without changing the character of the corresponding EWA
-% filter:
-%
-% 'No-Op' Vertical and Horizontal Line Preservation Condition:
-% Images with only vertical or horizontal features are preserved
-% when performing 'no-op" with EWA distortion.
-%
-% The Lanczos2 and Lanczos2Sharp filters are 2-lobe versions of the
-% Lanczos filters. The 'sharp' version uses a blur factor of
-% 0.9549963639785485, again chosen because the resulting EWA filter
-% comes as close as possible to satisfying the above
-% condition.
-%
-% Robidoux is another filter tuned for EWA. It is the Keys cubic
-% filter defined by B=(228 - 108 sqrt(2))/199. Robidoux satisfies the
-% "'No-Op' Vertical and Horizontal Line Preservation Condition"
-% exactly, and it moderately blurs high frequency 'pixel-hash'
-% patterns under no-op. It turns out to be close to both Mitchell
-% and Lanczos2Sharp. For example, its first crossing is at (36
-% sqrt(2) + 123)/(72 sqrt(2) + 47), almost the same as the first
-% crossing of Mitchell and Lanczos2Sharp.
-%
+% FIR filters are used as is, and are limited to that filters support window
+% (unless over-ridden). 'Gaussian' while classed as an IIR filter, is also
+% simply clipped by its support size (currently 1.5 or approximatally 3*sigma
+% as recommended by many references)
+%
+% The special a 'cylindrical' filter flag will promote the default 4-lobed
+% Windowed Sinc filter to a 3-lobed Windowed Jinc equivelent, which is better
+% suited to this style of image resampling. This typically happens when using
+% such a filter for images distortions.
+%
+% Directly requesting 'Sinc', 'Jinc' function as a filter will force the use
+% of function without any windowing, or promotion for cylindrical usage. This
+% is not recommended, except by image processing experts, especially as part
+% of expert option filter function selection.
+%
+% Two forms of the 'Sinc' function are available: Sinc and SincFast. Sinc is
+% computed using the traditional sin(pi*x)/(pi*x); it is selected if the user
+% specifically specifies the use of a Sinc filter. SincFast uses highly
+% accurate (and fast) polynomial (low Q) and rational (high Q) approximations,
+% and will be used by default in most cases.
+%
+% The Lanczos filter is a special 3-lobed Sinc-windowed Sinc filter (promoted
+% to Jinc-windowed Jinc for cylindrical (Elliptical Weighted Average) use).
+% The Sinc version is the most popular windowed filter.
+%
+% LanczosSharp is a slightly sharpened (blur=0.9812505644269356 < 1) form of
+% the Lanczos filter, specifically designed for EWA distortion (as a
+% Jinc-Jinc); it can also be used as a slightly sharper orthogonal Lanczos
+% (Sinc-Sinc) filter. The chosen blur value comes as close as possible to
+% satisfying the following condition without changing the character of the
+% corresponding EWA filter:
+%
+% 'No-Op' Vertical and Horizontal Line Preservation Condition: Images with
+% only vertical or horizontal features are preserved when performing 'no-op"
+% with EWA distortion.
+%
+% The Lanczos2 and Lanczos2Sharp filters are 2-lobe versions of the Lanczos
+% filters. The 'sharp' version uses a blur factor of 0.9549963639785485,
+% again chosen because the resulting EWA filter comes as close as possible to
+% satisfying the above condition.
+%
+% Robidoux is another filter tuned for EWA. It is the Keys cubic filter
+% defined by B=(228 - 108 sqrt(2))/199. Robidoux satisfies the "'No-Op'
+% Vertical and Horizontal Line Preservation Condition" exactly, and it
+% moderately blurs high frequency 'pixel-hash' patterns under no-op. It turns
+% out to be close to both Mitchell and Lanczos2Sharp. For example, its first
+% crossing is at (36 sqrt(2) + 123)/(72 sqrt(2) + 47), almost the same as the
+% first crossing of Mitchell and Lanczos2Sharp.
%
% 'EXPERT' OPTIONS:
%
-% These artifact "defines" are not recommended for production use
-% without expert knowledge of resampling, filtering, and the effects
-% they have on the resulting resampled (resize ro distorted) image.
+% These artifact "defines" are not recommended for production use without
+% expert knowledge of resampling, filtering, and the effects they have on the
+% resulting resampled (resize ro distorted) image.
%
% They can be used to override any and all filter default, and it is
-% recommended you make good use of "filter:verbose" to make sure that
-% the overall effect of your selection (before and after) is as
-% expected.
-%
-% "filter:verbose" controls whether to output the exact results of
-% the filter selections made, as well as plotting data for
-% graphing the resulting filter over the filters support range.
-%
-% "filter:filter" Select the main function associated with
-% this filter name, as the weighting function of the filter.
-% This can be used to set a windowing function as a weighting
-% function, for special purposes, such as graphing.
-%
-% If a "filter:window" operation has not been provided, then a
-% 'Box' windowing function will be set to denote that no
-% windowing function is being used.
-%
-% "filter:window" Select this windowing function for the filter.
-% While any filter could be used as a windowing function, using
-% the 'first lobe' of that filter over the whole support
-% window, using a non-windowing function is not advisible. If
-% no weighting filter function is specifed a 'SincFast' filter
-% will be used.
-%
-% "filter:lobes" Number of lobes to use for the Sinc/Jinc filter.
-% This a simpler method of setting filter support size that
-% will correctly handle the Sinc/Jinc switch for an operators
-% filtering requirements. Only integers should be given.
-%
-% "filter:support" Set the support size for filtering to the size
-% given This not recommended for Sinc/Jinc windowed filters
-% (lobes should be used instead). This will override any
-% 'filter:lobes' option.
-%
-% "filter:win-support" Scale windowing function to this size
-% instead. This causes the windowing (or self-windowing
-% Lagrange filter) to act is if the support window it much much
-% larger than what is actually supplied to the calling
-% operator. The filter however is still clipped to the real
-% support size given, by the support range suppiled to the
-% caller. If unset this will equal the normal filter support
-% size.
-%
-% "filter:blur" Scale the filter and support window by this amount.
-% A value >1 will generally result in a more burred image with
-% more ringing effects, while a value <1 will sharpen the
-% resulting image with more aliasing effects.
-%
-% "filter:sigma" The sigma value to use for the Gaussian filter
-% only. Defaults to '1/2'. Using a different sigme effectially
-% provides a method of using the filter as a 'blur' convolution.
-% Particularly when using it for Distort.
+% recommended you make good use of "filter:verbose" to make sure that the
+% overall effect of your selection (before and after) is as expected.
+%
+% "filter:verbose" controls whether to output the exact results of the
+% filter selections made, as well as plotting data for graphing the
+% resulting filter over the filters support range.
+%
+% "filter:filter" select the main function associated with this filter
+% name, as the weighting function of the filter. This can be used to
+% set a windowing function as a weighting function, for special
+% purposes, such as graphing.
+%
+% If a "filter:window" operation has not been provided, a 'Box'
+% windowing function will be set to denote that no windowing function is
+% being used.
+%
+% "filter:window" Select this windowing function for the filter. While any
+% filter could be used as a windowing function, using the 'first lobe' of
+% that filter over the whole support window, using a non-windowing
+% function is not advisible. If no weighting filter function is specifed
+% a 'SincFast' filter is used.
+%
+% "filter:lobes" Number of lobes to use for the Sinc/Jinc filter. This a
+% simpler method of setting filter support size that will correctly
+% handle the Sinc/Jinc switch for an operators filtering requirements.
+% Only integers should be given.
+%
+% "filter:support" Set the support size for filtering to the size given.
+% This not recommended for Sinc/Jinc windowed filters (lobes should be
+% used instead). This will override any 'filter:lobes' option.
+%
+% "filter:win-support" Scale windowing function to this size instead. This
+% causes the windowing (or self-windowing Lagrange filter) to act is if
+% the support window it much much larger than what is actually supplied
+% to the calling operator. The filter however is still clipped to the
+% real support size given, by the support range suppiled to the caller.
+% If unset this will equal the normal filter support size.
+%
+% "filter:blur" Scale the filter and support window by this amount. A value
+% > 1 will generally result in a more burred image with more ringing
+% effects, while a value <1 will sharpen the resulting image with more
+% aliasing effects.
+%
+% "filter:sigma" The sigma value to use for the Gaussian filter only.
+% Defaults to '1/2'. Using a different sigma effectively provides a
+% method of using the filter as a 'blur' convolution. Particularly when
+% using it for Distort.
%
% "filter:b"
-% "filter:c" Override the preset B,C values for a Cubic type of
-% filter If only one of these are given it is assumes to be a
-% 'Keys' type of filter such that B+2C=1, where Keys 'alpha'
-% value = C
+% "filter:c" Override the preset B,C values for a Cubic type of filter.
+% If only one of these are given it is assumes to be a 'Keys' type of
+% filter such that B+2C=1, where Keys 'alpha' value = C.
%
% Examples:
%
% -filter Lanczos
% -define filter:lobes=8
%
-%
% The format of the AcquireResizeFilter method is:
%
% ResizeFilter *AcquireResizeFilter(const Image *image,
%
% o image: the image.
%
-% o filter: the filter type, defining a preset filter, window and
-% support. The artifact settings listed above will override
-% those selections.
+% o filter: the filter type, defining a preset filter, window and support.
+% The artifact settings listed above will override those selections.
%
% o blur: blur the filter by this amount, use 1.0 if unknown. Image
-% artifact "filter:blur" will override this API call usage, including
-% any internal change (such as for cylindrical usage).
+% artifact "filter:blur" will override this API call usage, including any
+% internal change (such as for cylindrical usage).
%
-% o radial: use a 1D orthogonal filter (Sinc) or 2D cylindrical
-% (radial) filter (Jinc)
+% o radial: use a 1D orthogonal filter (Sinc) or 2D cylindrical (radial)
+% filter (Jinc).
%
% o exception: return any errors or warnings in this structure.
%
register ResizeFilter
*resize_filter;
-
/*
- Table Mapping given Filter, into Weighting and Windowing functions.
- A 'Box' windowing function means its a simble non-windowed filter.
- An 'SincFast' filter function could be upgraded to a 'Jinc' filter
- if a "cylindrical", unless a 'Sinc' or 'SincFast' filter was
- specifically requested.
+ Table Mapping given Filter, into Weighting and Windowing functions. A
+ 'Box' windowing function means its a simble non-windowed filter. An
+ 'SincFast' filter function could be upgraded to a 'Jinc' filter if a
+ "cylindrical", unless a 'Sinc' or 'SincFast' filter was specifically
+ requested.
- WARNING: The order of this tabel must match the order of the
- FilterTypes enumeration specified in "resample.h", or the filter
- names will not match the filter being setup.
+ WARNING: The order of this tabel must match the order of the FilterTypes
+ enumeration specified in "resample.h", or the filter names will not match
+ the filter being setup.
You can check filter setups with the "filter:verbose" setting.
*/
{ RobidouxFilter, BoxFilter }, /* Cubic Keys tuned for EWA */
};
/*
- Table mapping the filter/window from the above table to an actual
- function. The default support size for that filter as a weighting
- function, the range to scale with to use that function as a sinc
- windowing function, (typ 1.0).
+ Table mapping the filter/window from the above table to an actual function.
+ The default support size for that filter as a weighting function, the range
+ to scale with to use that function as a sinc windowing function, (typ 1.0).
Note that the filter_type -> function is 1 to 1 except for Sinc(),
- SincFast(), and CubicBC() functions, which may have multiple
- filter to function associations.
+ SincFast(), and CubicBC() functions, which may have multiple filter to
+ function associations.
- See "filter:verbose" handling below for the function -> filter
- mapping.
+ See "filter:verbose" handling below for the function -> filter mapping.
*/
static struct
{
/*
The known zero crossings of the Jinc() or more accurately the Jinc(x*PI)
function being used as a filter. It is used by the "filter:lobes" expert
- setting and for 'lobes' for Jinc functions in the previous table. This
- way users do not have to deal with the highly irrational lobe sizes of the
- Jinc filter.
+ setting and for 'lobes' for Jinc functions in the previous table. This way
+ users do not have to deal with the highly irrational lobe sizes of the Jinc
+ filter.
Values taken from
- http://cose.math.bas.bg/webMathematica/webComputing/BesselZeros.jsp
- using Jv-function with v=1, then dividing by PI.
+ http://cose.math.bas.bg/webMathematica/webComputing/BesselZeros.jsp using
+ Jv-function with v=1, then dividing by PI.
*/
static MagickRealType
jinc_zeros[16] =
(void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
assert(exception != (ExceptionInfo *) NULL);
assert(exception->signature == MagickSignature);
- minify_image=ResizeImage(image,image->columns/2,image->rows/2,CubicFilter,
- 1.0,exception);
+ minify_image=ResizeImage(image,image->columns/2,image->rows/2,CubicFilter,1.0,
+ exception);
return(minify_image);
}
\f
projects / imagemagick / commitdiff