$newimg = $img->copy();
- $newimg = $img->scale(xpixels=>400);
+ $newimg = $img->scale(xpixels=>400, qtype => 'mixing');
$newimg = $img->scale(xpixels=>400, ypixels=>400);
- $newimg = $img->scale(xpixels=>400, ypixels=>400, type=>min);
+ $newimg = $img->scale(xpixels=>400, ypixels=>400, type=>'min');
$newimg = $img->scale(scalefactor=>0.25);
+ $newimg = $img->scaleX(pixels=>400);
+ $newimg = $img->scaleX(scalefactor=>0.25);
+ $newimg = $img->scaleY(pixels=>400);
+ $newimg = $img->scaleY(scalefactor=>0.25);
+
$newimg = $img->crop(left=>50, right=>100, top=>10, bottom=>100);
$newimg = $img->crop(left=>50, top=>10, width=>50, height=>90);
$dest->paste(left=>40,top=>20,img=>$logo);
- $img->rubthrough(src=>$srcimage,tx=>30,ty=>50);
+ $img->rubthrough(src=>$srcimage,tx=>30, ty=>50);
+ $img->rubthrough(src=>$srcimage,tx=>30, ty=>50,
+ src_minx=>20, src_miny=>30,
+ src_maxx=>20, src_maxy=>30);
+ $img->compose(src => $src, tx => 30, ty => 20, combine => 'color');
+ $img->compose(src => $src, tx => 30, ty => 20, combine => 'color');
+ mask => $mask, opacity => 0.5);
$img->flip(dir=>"h"); # horizontal flip
$img->flip(dir=>"vh"); # vertical and horizontal flip
[ 1, 0, 0 ],
[ 0, 0, 1 ] ]);
+ # build an image using channels from multiple input images
+ $new = $img->combine(src => [ $im1, $im2, $im3 ]);
+ $new = $img->combine(src => [ $im1, $im2, $im3 ],
+ channels => [ 2, 1, 0 ]);
+
# limit the range of red channel from 0..255 to 0..127
@map = map { int( $_/2 } 0..255;
$img->map( red=>\@map );
Either they take an existing image and modify it in place, or they
return a modified copy.
-Functions that modify inplace are C<flip()>, C<paste()> and
-C<rubthrough()>. If the original is to be left intact it's possible
-to make a copy and alter the copy:
+Functions that modify inplace are C<flip()>, C<paste()>,
+C<rubthrough()> and C<compose()>. If the original is to be left
+intact it's possible to make a copy and alter the copy:
$flipped = $img->copy()->flip(dir=>'h');
=over
-=item copy
+=item copy()
-To create a copy of an image use the C<copy()> method. This is usefull
+To create a copy of an image use the C<copy()> method. This is useful
if you want to keep an original after doing something that changes the image.
$newimg = $orig->copy();
-=item scale
+=item scale()
-To scale an image so porportions are maintained use the
-C<$img-E<gt>scale()> method. if you give either a xpixels or ypixels
-parameter they will determine the width or height respectively. If
-both are given the one resulting in a larger image is used. example:
+X<scale>To scale an image so proportions are maintained use the
+C<$img-E<gt>scale()> method. if you give either a C<xpixels> or
+C<ypixels> parameter they will determine the width or height
+respectively. If both are given the one resulting in a larger image
+is used, unless you set the C<type> parameter to C<'min'>. example:
C<$img> is 700 pixels wide and 500 pixels tall.
$newimg = $img->scale(xpixels=>400); # 400x285
$newimg = $img->scale(ypixels=>400); # 560x400
$newimg = $img->scale(xpixels=>400,ypixels=>400); # 560x400
- $newimg = $img->scale(xpixels=>400,ypixels=>400,type=>min); # 400x285
+ $newimg = $img->scale(xpixels=>400,ypixels=>400,type=>'min'); # 400x285
+
+ $newimg = $img->scale(xpixels=>400, ypixels=>400),type=>'nonprop'); # 400x400
$newimg = $img->scale(scalefactor=>0.25); 175x125
$newimg = $img->scale(); # 350x250
-if you want to create low quality previews of images you can pass
+If you want to create low quality previews of images you can pass
C<qtype=E<gt>'preview'> to scale and it will use nearest neighbor
sampling instead of filtering. It is much faster but also generates
worse looking images - especially if the original has a lot of sharp
variations and the scaled image is by more than 3-5 times smaller than
the original.
-If you need to scale images per axis it is best to do it simply by
-calling scaleX and scaleY. You can pass either 'scalefactor' or
-'pixels' to both functions.
+=over
+
+=item *
+
+C<xpixels>, C<ypixels> - desired size of the scaled image. The
+C<type> parameter controls whether the larger or smaller of the two
+possible sizes is chosen, or if the image is scaled
+non-proportionally.
+
+=item *
+
+C<constrain> - an Image::Math::Constrain object defining the way in
+which the image size should be constrained.
+
+=item *
+
+C<scalefactor> - if none of C<xpixels>, C<ypixels>, C<xscalefactor>,
+C<yscalefactor> or C<constrain> is supplied then this is used as the
+ratio to scale by. Default: 0.5.
+
+=item *
+
+C<xscalefactor>, C<yscalefactor> - if both are supplied then the image is
+scaled as per these parameters, whether this is proportionally or not.
+New in Imager 0.54.
+
+=item *
+
+C<type> - controls whether the larger or smaller of the two possible
+sizes is chosen, possible values are:
+
+=over
+
+=item *
+
+C<min> - the smaller of the 2 sizes are chosen.
+
+=item *
+
+C<max> - the larger of the 2 sizes. This is the default.
+
+=item *
+
+C<nonprop> - non-proportional scaling. New in Imager 0.54.
+
+=back
+
+scale() will fail if C<type> is set to some other value.
+
+For example, if the original image is 400 pixels wide by 200 pixels
+high and C<xpixels> is set to 300, and C<ypixels> is set to 160. When
+C<type> is C<'min'> the resulting image is 300 x 150, when C<type> is
+C<'max'> the resulting image is 320 x 160.
+
+C<type> is only used if both C<xpixels> and C<ypixels> are supplied.
+
+=item *
+
+C<qtype> - defines the quality of scaling performed. Possible values are:
+
+=over
+
+=item *
+
+C<normal> - high quality scaling. This is the default.
+
+=item *
+
+C<preview> - lower quality. When scaling down this will skip input
+pixels, eg. scaling by 0.5 will skip every other pixel. When scaling
+up this will duplicate pixels.
+
+=item *
+
+C<mixing> - implements the mixing algorithm implemented by
+F<pnmscale>. This retains more detail when scaling down than
+C<normal>. When scaling down this proportionally accumulates sample
+data from the pixels, resulting in a proportional mix of all of the
+pixels. When scaling up this will mix pixels when the sampling grid
+crosses a pixel boundary but will otherwise copy pixel values.
+
+=back
+
+scale() will fail if C<qtype> is set to some other value.
+
+C<preview> is faster than C<mixing> which is much faster than C<normal>.
+
+=back
+
+To scale an image on a given axis without maintaining proportions, it
+is best to call the scaleX() and scaleY() methods with the required
+dimensions. eg.
+
+ my $scaled = $img->scaleX(pixels=>400)->scaleY(pixels=>200);
+
+From Imager 0.54 you can scale without maintaining proportions either
+by supplying both the C<xscalefactor> and C<yscalefactor> arguments:
+
+ my $scaled = $img->scale(xscalefactor => 0.5, yscalefactor => 0.67);
+
+or by supplying C<xpixels> and C<ypixels> and setting C<type> to
+<nonprop>:
+
+ my $scaled = $im->scale(xpixels => 200, ypixels => 200, type => 'nonprop');
+
+Returns a new scaled image on success. The source image is not
+modified.
+
+Returns false on failure, check the errstr() method for the reason for
+failure.
+
+A mandatory warning is produced if scale() is called in void context.
+
+ # setup
+ my $image = Imager->new;
+ $image->read(file => 'somefile.jpg')
+ or die $image->errstr;
+
+ # all full quality unless indicated otherwise
+ # half the size:
+ my $half = $image->scale;
+
+ # double the size
+ my $double = $image->scale(scalefactor => 2.0);
+
+ # so a 400 x 400 box fits in the resulting image:
+ my $fit400x400inside = $image->scale(xpixels => 400, ypixels => 400);
+ my $fit400x400inside2 = $image->scale(xpixels => 400, ypixels => 400,
+ type=>'max');
+
+ # fit inside a 400 x 400 box
+ my $inside400x400 = $image->scale(xpixels => 400, ypixels => 400,
+ type=>'min');
+
+ # make it 400 pixels wide or high
+ my $width400 = $image->scale(xpixels => 400);
+ my $height400 = $image->scale(ypixels => 400);
+
+ # low quality scales:
+ # to half size
+ my $low = $image->scale(qtype => 'preview');
+
+ # mixing method scale
+ my $mixed = $image->scale(qtype => 'mixing', scalefactor => 0.1);
+
+ # using an Image::Math::Constrain object
+ use Image::Math::Constrain;
+ my $constrain = Image::Math::Constrain->new(800, 600);
+ my $scaled = $image->scale(constrain => $constrain);
+
+ # same as Image::Math::Constrain version
+ my $scaled2 = $image->scale(xpixels => 800, ypixels => 600, type => 'min');
+
+=item scaleX()
-=item crop
+scaleX() will scale along the X dimension, return a new image with the
+new width:
+
+ my $newimg = $img->scaleX(pixels=>400); # 400x500
+ $newimg = $img->scaleX(scalefactor=>0.25) # 175x500
+
+=over
+
+=item *
+
+C<scalefactor> - the amount to scale the X axis. Ignored if C<pixels> is
+provided. Default: 0.5.
+
+=item *
+
+C<pixels> - the new width of the image.
+
+=back
+
+Returns a new scaled image on success. The source image is not
+modified.
+
+Returns false on failure, check the errstr() method for the reason for
+failure.
+
+A mandatory warning is produced if scaleX() is called in void context.
+
+=item scaleY()
+
+scaleY() will scale along the Y dimension, return a new image with the
+new height:
+
+ $newimg = $img->scaleY(pixels=>400); # 700x400
+ $newimg = $img->scaleY(scalefactor=>0.25) # 700x125
+
+=over
+
+=item *
+
+C<scalefactor> - the amount to scale the Y axis. Ignored if C<pixels> is
+provided. Default: 0.5.
+
+=item *
+
+C<pixels> - the new height of the image.
+
+=back
+
+Returns a new scaled image on success. The source image is not
+modified.
+
+Returns false on failure, check the errstr() method for the reason for
+failure.
+
+A mandatory warning is produced if scaleY() is called in void context.
+
+=item scale_calculate()
+
+Performs the same calculations that the scale() method does to
+calculate the scaling factors from the parameters you pass.
+
+scale_calculate() can be called as an object method, or as a class
+method.
+
+Takes the following parameters over scale():
+
+=over
+
+=item *
+
+C<width>, C<height> - the image width and height to base the scaling on.
+Required if scale_calculate() is called as a class method. If called
+as an object method these default to the image width and height
+respectively.
+
+=back
+
+You might use scale_calculate() as a class method when generating an
+HTML C<IMG> tag, for example.
+
+Returns an empty list on failure.
+
+Returns a list containing horizontal scale factor, vertical scale
+factor, new width, new height, on success.
+
+ my ($x_scale, $y_scale, $new_width, $new_height) =
+ Imager->scale_calculate(width => 1024, height => 768,
+ ypixels => 180, type => 'min');
+
+ my ($x_scale, $y_scale, $new_width, $new_height) =
+ $img->scale_calculate(xpixels => 200, type => 'min');
+
+=item crop()
+
+=for stopwords resize
Another way to resize an image is to crop it. The parameters to
crop are the edges of the area that you want in the returned image,
where the right and bottom edges are non-inclusive. If a parameter is
omitted a default is used instead.
- # the first two produce the same image
+crop() returns the cropped image and does not modify the source image.
+
+The possible parameters are:
+
+=over
+
+=item *
+
+C<left> - the left edge of the area to be cropped. Default: 0
+
+=item *
+
+C<top> - the top edge of the area to be cropped. Default: 0
+
+=item *
+
+C<right> - the right edge of the area to be cropped. Default: right
+edge of image.
+
+=item *
+
+C<bottom> - the bottom edge of the area to be cropped. Default:
+bottom edge of image.
+
+=item *
+
+C<width> - width of the crop area. Ignored if both C<left> and C<right> are
+supplied. Centered on the image if neither C<left> nor C<right> are
+supplied.
+
+=item *
+
+C<height> - height of the crop area. Ignored if both C<top> and
+C<bottom> are supplied. Centered on the image if neither C<top> nor
+C<bottom> are supplied.
+
+=back
+
+For example:
+
+ # these produce the same image
$newimg = $img->crop(left=>50, right=>100, top=>10, bottom=>100);
$newimg = $img->crop(left=>50, top=>10, width=>50, height=>90);
- $newimg = $img->crop(left=>50, right=>100); # top
+ $newimg = $img->crop(right=>100, bottom=>100, width=>50, height=>90);
+
+ # and the following produce the same image
+ $newimg = $img->crop(left=>50, right=>100);
+ $newimg = $img->crop(left=>50, right=>100, top=>0,
+ bottom=>$img->getheight);
+
+ # grab the top left corner of the image
+ $newimg = $img->crop(right=>50, bottom=>50);
You can also specify width and height parameters which will produce a
new image cropped from the center of the input image, with the given
$newimg = $img->crop(width=>50, height=>50);
-The width and height parameters take precedence over the left/right
-and top/bottom parameters respectively.
+If you supply C<left>, C<width> and C<right> values, the C<right>
+value will be ignored. If you supply C<top>, C<height> and C<bottom>
+values, the C<bottom> value will be ignored.
-=item rotate
+The edges of the cropped area default to the edges of the source
+image, for example:
+
+ # a vertical bar from the middle from top to bottom
+ $newimg = $img->crop(width=>50);
+
+ # the right half
+ $newimg = $img->crop(left=>$img->getwidth() / 2);
+
+If the resulting image would have zero width or height then crop()
+returns false and $img->errstr is an appropriate error message.
+
+A mandatory warning is produced if crop() is called in void context.
+
+=item rotate()
Use the rotate() method to rotate an image. This method will return a
new, rotated image.
my $rotpi4 = $img->rotate(radians=>3.14159265/4);
Exact image rotation uses the same underlying transformation engine as
-the matrix_transform() method.
+the matrix_transform() method (see Imager::Engines).
+
+You can also supply a C<back> argument which acts as a background
+color for the areas of the image with no samples available (outside
+the rectangle of the source image.) This can be either an
+Imager::Color or Imager::Color::Float object. This is B<not> mixed
+transparent pixels in the middle of the source image, it is B<only>
+used for pixels where there is no corresponding pixel in the source
+image.
To rotate in steps of 90 degrees, use the 'right' parameter:
Rotations are clockwise for positive values.
+Parameters:
+
+=over
+
+=item *
+
+C<right> - rotate by an exact multiple of 90 degrees, specified in
+degrees.
+
+=item *
+
+C<radians> - rotate by an angle specified in radians.
+
+=item *
+
+C<degrees> - rotate by an angle specified in degrees.
+
+=item *
+
+C<back> - for C<radians> and C<degrees> this is the color used for the
+areas not covered by the original image. For example, the corners of
+an image rotated by 45 degrees.
+
+This can be either an Imager::Color object, an Imager::Color::Float
+object or any parameter that Imager can convert to a color object, see
+L<Imager::Draw/Color Parameters> for details.
+
+This is B<not> mixed transparent pixels in the middle of the source
+image, it is B<only> used for pixels where there is no corresponding
+pixel in the source image.
+
+Default: transparent black.
+
=back
+ # rotate 45 degrees clockwise,
+ my $rotated = $img->rotate(degrees => 45);
-=head2 Image pasting/flipping/
+ # rotate 10 degrees counter-clockwise
+ # set pixels not sourced from the original to red
+ my $rotated = $img->rotate(degrees => -10, back => 'red');
+
+=back
+
+=head2 Image pasting/flipping
A list of the transformations that alter the source image follows:
=over
-=item paste
+=item paste()
+X<paste>To copy an image to onto another image use the C<paste()>
+method.
-To copy an image to onto another image use the C<paste()> method.
-
- $dest->paste(left=>40,top=>20,img=>$logo);
+ $dest->paste(left=>40, top=>20, src=>$logo);
That copies the entire C<$logo> image onto the C<$dest> image so that the
upper left corner of the C<$logo> image is at (40,20).
+Parameters:
-=item rubthrough
+=over
+
+=item *
+
+C<src>, C<img> - the source image. C<src> added for compatibility with
+rubthrough().
+
+=item *
+
+C<left>, C<top> - position in output of the top left of the pasted image.
+Default: (0,0)
+
+=item *
+
+C<src_minx>, C<src_miny> - the top left corner in the source image to start
+the paste from. Default: (0, 0)
+
+=item *
+
+C<src_maxx>, C<src_maxy> - the bottom right in the source image of the sub
+image to paste. This position is B<non> inclusive. Default: bottom
+right corner of the source image.
+
+=item *
+
+C<width>, C<height> - if the corresponding src_maxx or src_maxy is not
+defined then width or height is used for the width or height of the
+sub image to be pasted.
+
+=back
+
+ # copy the 20x20 pixel image from (20,20) in $src_image to (10,10) in $img
+ $img->paste(src=>$src_image,
+ left => 10, top => 10,
+ src_minx => 20, src_miny => 20,
+ src_maxx => 40, src_maxx => 40);
+
+If the source image has an alpha channel and the target doesn't, then
+the source is treated as if composed onto a black background.
+
+If the source image is color and the target is gray scale, the
+source is treated as if run through C<< convert(preset=>'gray') >>.
+
+=item rubthrough()
A more complicated way of blending images is where one image is
put 'over' the other with a certain amount of opaqueness. The
-method that does this is rubthrough.
+method that does this is rubthrough().
+
+ $img->rubthrough(src=>$overlay,
+ tx=>30, ty=>50,
+ src_minx=>20, src_miny=>30,
+ src_maxx=>20, src_maxy=>30);
+
+That will take the sub image defined by I<$overlay> and
+I<[src_minx,src_maxx)[src_miny,src_maxy)> and overlay it on top of
+I<$img> with the upper left corner at (30,50). You can rub 2 or 4
+channel images onto a 3 channel image, or a 2 channel image onto a 1
+channel image. The last channel is used as an alpha channel. To add
+an alpha channel to an image see I<convert()>.
+
+Parameters:
+
+=over
+
+=item *
+
+C<tx>, C<ty> - location in the target image ($self) to render the
+top left corner of the source.
+
+=item *
+
+C<src_minx>, C<src_miny> - the top left corner in the source to transfer to
+the target image. Default: (0, 0).
+
+=item *
+
+C<src_maxx>, C<src_maxy> - the bottom right in the source image of the sub
+image to overlay. This position is B<non> inclusive. Default: bottom
+right corner of the source image.
+
+=back
+
+ # overlay all of $source onto $targ
+ $targ->rubthrough(tx => 20, ty => 25, src => $source);
+
+ # overlay the top left corner of $source onto $targ
+ $targ->rubthrough(tx => 20, ty => 25, src => $source,
+ src_maxx => 20, src_maxy => 20);
+
+ # overlay the bottom right corner of $source onto $targ
+ $targ->rubthrough(tx => 20, ty => 30, src => $src,
+ src_minx => $src->getwidth() - 20,
+ src_miny => $src->getheight() - 20);
+
+rubthrough() returns true on success. On failure check
+C<< $target->errstr >> for the reason for failure.
+
+=item compose()
+
+Draws the source image over the target image, with the source alpha
+channel modified by the optional mask and the opacity.
+
+ $img->compose(src=>$overlay,
+ tx=>30, ty=>50,
+ src_minx=>20, src_miny=>30,
+ src_maxx=>20, src_maxy=>30,
+ mask => $mask, opacity => 0.5);
+
+That will take the sub image defined by I<$overlay> and
+I<[src_minx,src_maxx)[src_miny,src_maxy)> and overlay it on top of
+I<$img> with the upper left corner at (30,50). You can rub 2 or 4
+channel images onto a 3 channel image, or a 2 channel image onto a 1
+channel image.
- $img->rubthrough(src=>$srcimage,tx=>30,ty=>50);
+Parameters:
-That will take the image C<$srcimage> and overlay it with the upper
-left corner at (30,50). You can rub 2 or 4 channel images onto a 3
-channel image, or a 2 channel image onto a 1 channel image. The last
-channel is used as an alpha channel.
+=over
+
+=item *
+
+C<src> - the source image to draw onto the target. Required.
+
+=item *
+
+C<tx>, C<ty> - location in the target image ($self) to render the top
+left corner of the source. These can also be supplied as C<left> and
+C<right>. Default: (0, 0).
+
+=item *
+
+C<src_minx>, C<src_miny> - the top left corner in the source to transfer to
+the target image. Default: (0, 0).
+
+=item *
+
+C<src_maxx>, C<src_maxy> - the bottom right in the source image of the sub
+image to overlay. This position is B<non> inclusive. Default: bottom
+right corner of the source image.
+
+=item *
+
+C<mask> - a mask image. The first channel of this image is used to
+modify the alpha channel of the source image. This can be used to
+mask out portions of the source image. Where the first channel is
+zero none of the source image will be used, where the first channel is
+maximum the full alpha of the source image will be used, as further
+modified by the opacity.
+
+=item *
+
+opacity - further modifies the alpha channel of the source image, in
+the range 0.0 to 1.0. Default: 1.0.
+=item *
+
+combine - the method to combine the source pixels with the target.
+See the combine option documentation in Imager::Fill. Default:
+normal.
+
+=back
+
+Calling compose() with no mask, combine set to C<normal>, opacity set
+to C<1.0> is equivalent to calling rubthrough().
+
+compose() is intended to be produce similar effects to layers in
+interactive paint software.
+
+ # overlay all of $source onto $targ
+ $targ->compose(tx => 20, ty => 25, src => $source);
+
+ # overlay the top left corner of $source onto $targ
+ $targ->compose(tx => 20, ty => 25, src => $source,
+ src_maxx => 20, src_maxy => 20);
+
+ # overlay the bottom right corner of $source onto $targ
+ $targ->compose(tx => 20, ty => 30, src => $src,
+ src_minx => $src->getwidth() - 20,
+ src_miny => $src->getheight() - 20);
+
+compose() returns true on success. On failure check $target->errstr
+for the reason for failure.
-=item flip
+=item flip()
An inplace horizontal or vertical flip is possible by calling the
C<flip()> method. If the original is to be preserved it's possible to
$img->flip(dir=>"vh"); # vertical and horizontal flip
$nimg = $img->copy->flip(dir=>"v"); # make a copy and flip it vertically
-=back
+flip() returns true on success. On failure check $img->errstr for the
+reason for failure.
+=back
+=head2 Color transformations
+=over
-=head2 Color transformations
+=item convert()
You can use the convert method to transform the color space of an
image using a matrix. For ease of use some presets are provided.
=item *
-convert an RGB or RGBA image to grayscale.
+convert an RGB or RGBA image to gray scale.
=item *
-convert a grayscale image to RGB.
+convert a gray scale image to RGB.
=item *
=over
-=item gray
-
-=item grey
+=item *
-converts an RGBA image into a grayscale image with alpha channel, or
-an RGB image into a grayscale image without an alpha channel.
+C<gray>, C<grey> - converts an RGBA image into a gray scale image with
+alpha channel, or an RGB image into a gray scale image without an
+alpha channel.
This weights the RGB channels at 22.2%, 70.7% and 7.1% respectively.
-=item noalpha
-
-removes the alpha channel from a 2 or 4 channel image. An identity
-for other images.
-
-=item red
-
-=item channel0
+=item *
-extracts the first channel of the image into a single channel image
+C<noalpha> - removes the alpha channel from a 2 or 4 channel image.
+An identity for other images.
-=item green
+=item *
-=item channel1
+C<red>, C<channel0> - extracts the first channel of the image into a
+single channel image
-extracts the second channel of the image into a single channel image
+=item *
-=item blue
+C<green>, C<channel1> - extracts the second channel of the image into
+a single channel image
-=item channel2
+=item *
-extracts the third channel of the image into a single channel image
+C<blue>, C<channel2> - extracts the third channel of the image into a
+single channel image
-=item alpha
+=item *
-extracts the alpha channel of the image into a single channel image.
+C<alpha> - extracts the alpha channel of the image into a single
+channel image.
-If the image has 1 or 3 channels (assumed to be grayscale of RGB) then
+If the image has 1 or 3 channels (assumed to be gray scale or RGB) then
the resulting image will be all white.
-=item rgb
+=item *
-converts a grayscale image to RGB, preserving the alpha channel if any
+C<rgb>
-=item addalpha
+converts a gray scale image to RGB, preserving the alpha channel if any
-adds an alpha channel to a grayscale or RGB image. Preserves an
-existing alpha channel for a 2 or 4 channel image.
+=item *
+
+C<addalpha> - adds an alpha channel to a gray scale or RGB image.
+Preserves an existing alpha channel for a 2 or 4 channel image.
=back
-For example, to convert an RGB image into a greyscale image:
+For example, to convert an RGB image into a gray scale image:
$new = $img->convert(preset=>'grey'); # or gray
-or to convert a grayscale image to an RGB image:
+or to convert a gray scale image to an RGB image:
$new = $img->convert(preset=>'rgb');
The presets aren't necessary simple constants in the code, some are
generated based on the number of channels in the input image.
-If you want to perform some other colour transformation, you can use
+If you want to perform some other color transformation, you can use
the 'matrix' parameter.
For each output pixel the following matrix multiplication is done:
[ 1, 0, 0 ],
[ 0, 0, 1 ] ]);
-or to convert a 3 channel image to greyscale using equal weightings:
+or to convert a 3 channel image to gray scale using equal weightings:
$new = $img->convert(matrix=>[ [ 0.333, 0.333, 0.334 ] ])
+Convert a 2 channel image (gray scale with alpha) to an RGBA image with
+the gray converted to the specified RGB color:
+
+ # set (RGB) scaled on the grey scale portion and copy the alpha
+ # channel as is
+ my $colored = $gray->convert(matrix=>[ [ ($red/255), 0 ],
+ [ ($green/255), 0 ],
+ [ ($blue/255), 0 ],
+ [ 0, 1 ],
+ ]);
+
+To convert a 3 channel image to a 4 channel image with a 50 percent
+alpha channel:
+
+ my $withalpha = $rgb->convert(matrix =>[ [ 1, 0, 0, 0 ],
+ [ 0, 1, 0, 0 ],
+ [ 0, 0, 1, 0 ],
+ [ 0, 0, 0, 0.5 ],
+ ]);
+
+=item combine()
+X<combine>
+
+Combine channels from one or more input images into a new image.
+
+Parameters:
+
+=over
+
+=item *
+
+C<src> - a reference to an array of input images. There must be at least
+one input image. A given image may appear more than once in C<src>.
+
+=item *
+
+C<channels> - a reference to an array of channels corresponding to the
+source images. If C<channels> is not supplied then the first channel
+from each input image is used. If the array referenced by C<channels>
+is shorter than that referenced by C<src> then the first channel is
+used from the extra images.
+
+=back
+
+ # make an rgb image from red, green, and blue images
+ my $rgb = Imager->combine(src => [ $red, $green, $blue ]);
+
+ # convert a BGR image into RGB
+ my $rgb = Imager->combine(src => [ $bgr, $bgr, $bgr ],
+ channels => [ 2, 1, 0 ]);
+
+ # add an alpha channel from another image
+ my $rgba = Imager->combine(src => [ $rgb, $rgb, $rgb, $alpha ],
+ channels => [ 0, 1, 2, 0 ]);
+
+=back
=head2 Color Mappings
+=over
+
+=item map()
+
You can use the map method to map the values of each channel of an
-image independently using a list of lookup tables. It's important to
+image independently using a list of look-up tables. It's important to
realize that the modification is made inplace. The function simply
returns the input image again or undef on failure.
-Each channel is mapped independently through a lookup table with 256
+Each channel is mapped independently through a look-up table with 256
entries. The elements in the table should not be less than 0 and not
greater than 255. If they are out of the 0..255 range they are
clamped to the range. If a table does not contain 256 entries it is
unaffected.
It is also possible to simply specify an array of maps that are
-applied to the images in the rgba order. For example to apply
+applied to the images in the RGBA order. For example to apply
maps to the C<red> and C<blue> channels one would use:
$img->map(maps=>[\@redmap, [], \@bluemap]);
+=back
+
+=head1 SEE ALSO
+
+L<Imager>, L<Imager::Engines>
+
+=head1 AUTHOR
+Tony Cook <tonyc@cpan.org>, Arnar M. Hrafnkelsson
+=head1 REVISION
+$Revision$
+=cut
projects / imager.git / blobdiff