1Imager::TransformationsU(s3e)r Contributed Perl DocumentaItmiaogner::Transformations(3)
2
6 Imager::Transformations - Simple transformations of one image into
7 another.
8
10 use Imager;
11 $newimg = $img->copy();
13 $newimg = $img->scale(xpixels=>400, qtype => 'mixing');
15 $newimg = $img->scale(xpixels=>400, ypixels=>400);
16 $newimg = $img->scale(xpixels=>400, ypixels=>400, type=>'min');
17 $newimg = $img->scale(scalefactor=>0.25);
18 $newimg = $img->scaleX(pixels=>400);
20 $newimg = $img->scaleX(scalefactor=>0.25);
21 $newimg = $img->scaleY(pixels=>400);
22 $newimg = $img->scaleY(scalefactor=>0.25);
23 $newimg = $img->crop(left=>50, right=>100, top=>10, bottom=>100);
25 $newimg = $img->crop(left=>50, top=>10, width=>50, height=>90);
26 $dest->paste(left=>40,top=>20,img=>$logo);
28 $img->rubthrough(src=>$srcimage,tx=>30, ty=>50);
30 $img->rubthrough(src=>$srcimage,tx=>30, ty=>50,
31 src_minx=>20, src_miny=>30,
32 src_maxx=>20, src_maxy=>30);
33 $img->compose(src => $src, tx => 30, ty => 20, combine => 'color');
35 $img->compose(src => $src, tx => 30, ty => 20, combine => 'color');
36 mask => $mask, opacity => 0.5);
37 $img->flip(dir=>"h"); # horizontal flip
39 $img->flip(dir=>"vh"); # vertical and horizontal flip
40 $newimg = $img->copy->flip(dir=>"v"); # make a copy and flip it vertically
41 my $rot20 = $img->rotate(degrees=>20);
43 my $rotpi4 = $img->rotate(radians=>3.14159265/4);
44 # Convert image to gray
46 $new = $img->convert(preset=>'grey');
47 # Swap red/green channel
49 $new = $img->convert(matrix=>[ [ 0, 1, 0 ],
50 [ 1, 0, 0 ],
51 [ 0, 0, 1 ] ]);
52 # limit the range of red channel from 0..255 to 0..127
54 @map = map { int( $_/2 } 0..255;
55 $img->map( red=>\@map );
56 # Apply a Gamma of 1.4
58 my $gamma = 1.4;
59 my @map = map { int( 0.5 + 255*($_/255)**$gamma ) } 0..255;
60 $img->map(all=>\@map); # inplace conversion
61
63 The methods described in Imager::Transformations fall into two cate‐
64 gories. Either they take an existing image and modify it in place, or
65 they return a modified copy.
66 Functions that modify inplace are "flip()", "paste()", "rubthrough()"
68 and "compose()". If the original is to be left intact it's possible to
69 make a copy and alter the copy:
70 $flipped = $img->copy()->flip(dir=>'h');
72 Image copying/resizing/cropping/rotating
74 A list of the transformations that do not alter the source image fol‐
76 lows:
77 copy
79 To create a copy of an image use the "copy()" method. This is use‐
80 full if you want to keep an original after doing something that
81 changes the image.
82 $newimg = $orig->copy();
84 scale
86 To scale an image so porportions are maintained use the
87 "$img->scale()" method. if you give either a xpixels or ypixels
88 parameter they will determine the width or height respectively. If
89 both are given the one resulting in a larger image is used, unless
90 you set the "type" parameter to 'min'. example: $img is 700 pixels
91 wide and 500 pixels tall.
92 $newimg = $img->scale(xpixels=>400); # 400x285
94 $newimg = $img->scale(ypixels=>400); # 560x400
95 $newimg = $img->scale(xpixels=>400,ypixels=>400); # 560x400
97 $newimg = $img->scale(xpixels=>400,ypixels=>400,type=>'min'); # 400x285
98 $newimg = $img->scale(xpixels=>400, ypixels=>400),type=>'nonprop'); # 400x400
100 $newimg = $img->scale(scalefactor=>0.25); 175x125
102 $newimg = $img->scale(); # 350x250
103 If you want to create low quality previews of images you can pass
105 "qtype=>'preview'" to scale and it will use nearest neighbor sam‐
106 pling instead of filtering. It is much faster but also generates
107 worse looking images - especially if the original has a lot of
108 sharp variations and the scaled image is by more than 3-5 times
109 smaller than the original.
110 * xpixels, ypixels - desired size of the scaled image. The
112 "type" parameter controls whether the larger or smaller of the
113 two possible sizes is chosen, or if the image is scaled
114 non-proportionally.
115 * constrain - an Image::Math::Constrain object defining the way
117 in which the image size should be constrained.
118 * scalefactor - if none of xpixels, ypixels, xscalefactor,
120 yscalefactor or constrain is supplied then this is used as the
121 ratio to scale by. Default: 0.5.
122 * xscalefactor, yscalefactor - if both are supplied then the
124 image is scaled as per these parameters, whether this is pro‐
125 portionally or not. New in Imager 0.54.
126 * type - controls whether the larger or smaller of the two possi‐
128 ble sizes is chosen, possible values are:
129 * min - the smaller of the 2 sizes are chosen.
131 * max - the larger of the 2 sizes. This is the default.
133 * nonprop - non-proportional scaling. New in Imager 0.54.
135 scale() will fail if "type" is set to some other value.
137 For example, if the original image is 400 pixels wide by 200
139 pixels high and "xpixels" is set to 300, and "ypixels" is set
140 to 160. When "type" is 'min' the resulting image is 300 x 150,
141 when "type" is 'max' the resulting image is 320 x 150.
142 "type" is only used if both "xpixels" and "ypixels" are sup‐
144 plied.
145 * qtype - defines the quality of scaling performed. Possible
147 values are:
148 * "normal" - high quality scaling. This is the default.
150 * "preview" - lower quality. When scaling down this will
152 skip input pixels, eg. scaling by 0.5 will skip every other
153 pixel. When scaling up this will duplicate pixels.
154 * "mixing" - implements the mixing algorithm implemented by
156 pnmscale. This retains more detail when scaling down than
157 "normal". When scaling down this proportionally accumu‐
158 lates sample data from the pixels, resulting in a propor‐
159 tional mix of all of the pixels. When scaling up this will
160 mix pixels when the sampling grid crosses a pixel boundary
161 but will otherwise copy pixel values.
162 scale() will fail if "qtype" is set to some other value.
164 "preview" is faster than "mixing" which is much faster than
166 "normal".
167 To scale an image on a given axis without maintaining proportions,
169 it is best to call the scaleX() and scaleY() methods with the
170 required dimensions. eg.
171 my $scaled = $img->scaleX(pixels=>400)->scaleY(pixels=>200);
173 From Imager 0.54 you can scale without maintaining proportions
175 either by supplying both the xscalefactor and yscalefactor argu‐
176 ments:
177 my $scaled = $img->scale(xscalefactor => 0.5, yscalefactor => 0.67);
179 or by supplying "xpixels" and "ypixels" and setting "type" to "non‐
181 prop":
182 my $scaled = $im->scale(xpixels => 200, ypixels => 200, type => 'nonprop');
184 Returns a new scaled image on success. The source image is not
186 modified.
187 Returns false on failure, check the errstr() method for the reason
189 for failure.
190 A mandatory warning is produced if scale() is called in void con‐
192 text.
193 # setup
195 my $image = Imager->new;
196 $image->read(file => 'somefile.jpg')
197 or die $image->errstr;
198 # all full quality unless indicated otherwise
200 # half the size:
201 my $half = $image->scale;
202 # double the size
204 my $double = $image->scale(scalefactor => 2.0);
205 # so a 400 x 400 box fits in the resulting image:
207 my $fit400x400inside = $image->scale(xpixels => 400, ypixels => 400);
208 my $fit400x400inside2 = $image->scale(xpixels => 400, ypixels => 400,
209 type=>'max');
210 # fit inside a 400 x 400 box
212 my $inside400x400 = $image->scale(xpixels => 400, ypixels => 400,
213 type=>'min');
214 # make it 400 pixels wide or high
216 my $width400 = $image->scale(xpixels => 400);
217 my $height400 = $image->scale(ypixels => 400);
218 # low quality scales:
220 # to half size
221 my $low = $image->scale(qtype => 'preview');
222 # mixing method scale
224 my $mixed = $image->scale(qtype => 'mixing', scalefactor => 0.1);
225 # using an Image::Math::Constrain object
227 use Image::Math::Constrain;
228 my $constrain = Image::Math::Constrain->new(800, 600);
229 my $scaled = $image->scale(constrain => $constrain);
230 # same as Image::Math::Constrain version
232 my $scaled2 = $image->scale(xpixels => 800, ypixels => 600, type => 'min');
233 scaleX
235 scaleX() will scale along the X dimension, return a new image with
236 the new width:
237 my $newimg = $img->scaleX(pixels=>400); # 400x500
239 $newimg = $img->scaleX(scalefactor=>0.25) # 175x500
240 * scalefactor - the amount to scale the X axis. Ignored if "pix‐
242 els" is provided. Default: 0.5.
243 * pixels - the new width of the image.
245 Returns a new scaled image on success. The source image is not
247 modified.
248 Returns false on failure, check the errstr() method for the reason
250 for failure.
251 A mandatory warning is produced if scaleX() is called in void con‐
253 text.
254 scaleY
256 scaleY() will scale along the Y dimension, return a new image with
257 the new height:
258 $newimg = $img->scaleY(pixels=>400); # 700x400
260 $newimg = $img->scaleY(scalefactor=>0.25) # 700x125
261 * scalefactor - the amount to scale the Y axis. Ignored if "pix‐
263 els" is provided. Default: 0.5.
264 * pixels - the new height of the image.
266 Returns a new scaled image on success. The source image is not
268 modified.
269 Returns false on failure, check the errstr() method for the reason
271 for failure.
272 A mandatory warning is produced if scaleY() is called in void con‐
274 text.
275 scale_calculate
277 Performs the same calculations that the scale() method does to cal‐
278 culate the scaling factors from the parameters you pass.
279 scale_calculate() can be called as an object method, or as a class
281 method.
282 Takes the following parameters over scale():
284 * width, height - the image width and height to base the scaling
286 on. Required if scale_calculate() is called as a class method.
287 If called as an object method these default to the image width
288 and height respectively.
289 You might use scale_calculate() as a class method when generating
291 an IMG tag, for example.
292 Returns an empty list on failure.
294 Returns a list containing horizontal scale factor, vertical scale
296 factor, new width, new height, on success.
297 my ($x_scale, $y_scale, $new_width, $new_height) =
299 Imager->scale_calculate(width => 1024, height => 768,
300 ypixels => 180, type => 'min');
301 my ($x_scale, $y_scale, $new_width, $new_height) =
303 $img->scale_calculate(xpixels => 200, type => 'min');
304 crop
306 Another way to resize an image is to crop it. The parameters to
307 crop are the edges of the area that you want in the returned image,
308 where the right and bottom edges are non-inclusive. If a parameter
309 is omitted a default is used instead.
310 crop() returns the cropped image and does not modify the source
312 image.
313 The possible parameters are:
315 * "left" - the left edge of the area to be cropped. Default: 0
317 * "top" - the top edge of the area to be cropped. Default: 0
319 * "right" - the right edge of the area to be cropped. Default:
321 right edge of image.
322 * "bottom" - the bottom edge of the area to be cropped. Default:
324 bottom edge of image.
325 * "width" - width of the crop area. Ignored if both "left" and
327 "right" are supplied. Centered on the image if neither "left"
328 nor "right" are supplied.
329 * "height" - height of the crop area. Ignored if both "top" and
331 "bottom" are supplied. Centered on the image if neither "top"
332 nor "bottom" are supplied.
333 For example:
335 # these produce the same image
337 $newimg = $img->crop(left=>50, right=>100, top=>10, bottom=>100);
338 $newimg = $img->crop(left=>50, top=>10, width=>50, height=>90);
339 $newimg = $img->crop(right=>100, bottom=>100, width=>50, height=>90);
340 # and the following produce the same image
342 $newimg = $img->crop(left=>50, right=>100);
343 $newimg = $img->crop(left=>50, right=>100, top=>0,
344 bottom=>$img->getheight);
345 # grab the top left corner of the image
347 $newimg = $img->crop(right=>50, bottom=>50);
348 You can also specify width and height parameters which will produce
350 a new image cropped from the center of the input image, with the
351 given width and height.
352 $newimg = $img->crop(width=>50, height=>50);
354 If you supply "left", "width" and "right" values, the "right" value
356 will be ignored. If you supply "top", "height" and "bottom" val‐
357 ues, the "bottom" value will be ignored.
358 The edges of the cropped area default to the edges of the source
360 image, for example:
361 # a vertical bar from the middle from top to bottom
363 $newimg = $img->crop(width=>50);
364 # the right half
366 $newimg = $img->crop(left=>$img->getwidth() / 2);
367 If the resulting image would have zero width or height then crop()
369 returns false and $img->errstr is an appropriate error message.
370 A mandatory warning is produced if crop() is called in void con‐
372 text.
373 rotate
375 Use the rotate() method to rotate an image. This method will
376 return a new, rotated image.
377 To rotate by an exact amount in degrees or radians, use the
379 'degrees' or 'radians' parameter:
380 my $rot20 = $img->rotate(degrees=>20);
382 my $rotpi4 = $img->rotate(radians=>3.14159265/4);
383 Exact image rotation uses the same underlying transformation engine
385 as the matrix_transform() method (see Imager::Engines).
386 You can also supply a "back" argument which acts as a background
388 color for the areas of the image with no samples available (outside
389 the rectangle of the source image.) This can be either an
390 Imager::Color or Imager::Color::Float object. This is not mixed
391 transparent pixels in the middle of the source image, it is only
392 used for pixels where there is no corresponding pixel in the source
393 image.
394 To rotate in steps of 90 degrees, use the 'right' parameter:
396 my $rotated = $img->rotate(right=>270);
398 Rotations are clockwise for positive values.
400 Parameters:
402 * right - rotate by an exact multiple of 90 degrees, specified in
404 degreess.
405 * radians - rotate by an angle specified in radians.
407 * degrees - rotate by an angle specified in degrees.
409 * back - for "radians" and "degrees" this is the color used for
411 the areas not covered by the original image. For example, the
412 corners of an image rotated by 45 degrees.
413 This can be either an Imager::Color object, an
415 Imager::Color::Float object or any parameter that Imager can
416 convert to a color object, see "Color Parameters" in
417 Imager::Draw for details.
418 This is not mixed transparent pixels in the middle of the
420 source image, it is only used for pixels where there is no cor‐
421 responding pixel in the source image.
422 Default: transparent black.
424 # rotate 45 degrees clockwise,
426 my $rotated = $img->rotate(degrees => 45);
427 # rotate 10 degrees counter-clockwise
429 # set pixels not sourced from the original to red
430 my $rotated = $img->rotate(degrees => -10, back => 'red');
431 Image pasting/flipping
433 A list of the transformations that alter the source image follows:
435 paste
437 To copy an image to onto another image use the "paste()" method.
438 $dest->paste(left=>40, top=>20, src=>$logo);
440 That copies the entire $logo image onto the $dest image so that the
442 upper left corner of the $logo image is at (40,20).
443 Parameters:
445 * src, img - the source image. src added for compatibility with
447 rubthrough().
448 * left, top - position in output of the top left of the pasted
450 image. Default: (0,0)
451 * src_minx, src_miny - the top left corner in the source image to
453 start the paste from. Default: (0, 0)
454 * src_maxx, src_maxy - the bottom right in the source image of
456 the sub image to paste. This position is non inclusive.
457 Default: bottom right corner of the source image.
458 * width, height - if the corresponding src_maxx or src_maxy is
460 not defined then width or height is used for the width or
461 height of the sub image to be pasted.
462 # copy the 20x20 pixel image from (20,20) in $src_image to (10,10) in $img
464 $img->paste(src=>$src_image,
465 left => 10, top => 10,
466 src_minx => 20, src_miny => 20,
467 src_maxx => 40, src_maxx => 40);
468 If the source image has an alpha channel and the target doesn't,
470 then the source is treated as if composed onto a black background.
471 If the source image is color and the target is grayscale, the the
473 source is treated as if run through " convert(preset="'gray') >.
474 rubthrough
476 A more complicated way of blending images is where one image is put
477 'over' the other with a certain amount of opaqueness. The method
478 that does this is rubthrough.
479 $img->rubthrough(src=>$overlay,
481 tx=>30, ty=>50,
482 src_minx=>20, src_miny=>30,
483 src_maxx=>20, src_maxy=>30);
484 That will take the sub image defined by $overlay and
486 [src_minx,src_maxx)[src_miny,src_maxy) and overlay it on top of
487 $img with the upper left corner at (30,50). You can rub 2 or 4
488 channel images onto a 3 channel image, or a 2 channel image onto a
489 1 channel image. The last channel is used as an alpha channel. To
490 add an alpha channel to an image see convert().
491 Parameters:
493 * tx, ty - location in the the target image ($self) to render the
495 top left corner of the source.
496 * src_minx, src_miny - the top left corner in the source to
498 transfer to the target image. Default: (0, 0).
499 * src_maxx, src_maxy - the bottom right in the source image of
501 the sub image to overlay. This position is non inclusive.
502 Default: bottom right corner of the source image.
503 # overlay all of $source onto $targ
505 $targ->rubthrough(tx => 20, ty => 25, src => $source);
506 # overlay the top left corner of $source onto $targ
508 $targ->rubthrough(tx => 20, ty => 25, src => $source,
509 src_maxx => 20, src_maxy => 20);
510 # overlay the bottom right corner of $source onto $targ
512 $targ->rubthrough(tx => 20, ty => 30, src => $src,
513 src_minx => $src->getwidth() - 20,
514 src_miny => $src->getheight() - 20);
515 rubthrough() returns true on success. On failure check $tar‐
517 get->errstr for the reason for failure.
518 compose
520 Draws the source image over the target image, with the src alpha
521 channel modified by the optional mask and the opacity.
522 $img->compose(src=>$overlay,
524 tx=>30, ty=>50,
525 src_minx=>20, src_miny=>30,
526 src_maxx=>20, src_maxy=>30,
527 mask => $mask, opacity => 0.5);
528 That will take the sub image defined by $overlay and
530 [src_minx,src_maxx)[src_miny,src_maxy) and overlay it on top of
531 $img with the upper left corner at (30,50). You can rub 2 or 4
532 channel images onto a 3 channel image, or a 2 channel image onto a
533 1 channel image.
534 Parameters:
536 * src - the source image to draw onto the target. Required.
538 * tx, ty - location in the the target image ($self) to render the
540 top left corner of the source. These can also be supplied as
541 "left" and "right". Default: (0, 0).
542 * src_minx, src_miny - the top left corner in the source to
544 transfer to the target image. Default: (0, 0).
545 * src_maxx, src_maxy - the bottom right in the source image of
547 the sub image to overlay. This position is non inclusive.
548 Default: bottom right corner of the source image.
549 * mask - a mask image. The first channel of this image is used
551 to modify the alpha channel of the source image. This can me
552 used to mask out portions of the source image. Where the first
553 channel is zero none of the source image will be used, where
554 the first channel is max the full alpha of the source image
555 will be used, as further modified by the opacity.
556 * opacity - further modifies the alpha channel of the source
558 image, in the range 0.0 to 1.0. Default: 1.0.
559 * combine - the method to combine the source pixels with the tar‐
561 get. See the combine option documentation in Imager::Fill.
562 Default: normal.
563 Calling compose() with no mask, combine set to "normal", opacity
565 set to 1.0 is equivalent to calling rubthrough().
566 compose() is intended to be produce similar effects to layers in
568 interactive paint software.
569 # overlay all of $source onto $targ
571 $targ->compose(tx => 20, ty => 25, src => $source);
572 # overlay the top left corner of $source onto $targ
574 $targ->compose(tx => 20, ty => 25, src => $source,
575 src_maxx => 20, src_maxy => 20);
576 # overlay the bottom right corner of $source onto $targ
578 $targ->compose(tx => 20, ty => 30, src => $src,
579 src_minx => $src->getwidth() - 20,
580 src_miny => $src->getheight() - 20);
581 compose() returns true on success. On failure check $tar‐
583 get->errstr for the reason for failure.
584 flip
586 An inplace horizontal or vertical flip is possible by calling the
587 "flip()" method. If the original is to be preserved it's possible
588 to make a copy first. The only parameter it takes is the "dir"
589 parameter which can take the values "h", "v", "vh" and "hv".
590 $img->flip(dir=>"h"); # horizontal flip
592 $img->flip(dir=>"vh"); # vertical and horizontal flip
593 $nimg = $img->copy->flip(dir=>"v"); # make a copy and flip it vertically
594 flip() returns true on success. On failure check $img->errstr for
596 the reason for failure.
597 Color transformations
599 convert
601 You can use the convert method to transform the color space of an
602 image using a matrix. For ease of use some presets are provided.
603 The convert method can be used to:
605 * convert an RGB or RGBA image to grayscale.
607 * convert a grayscale image to RGB.
609 * extract a single channel from an image.
611 * set a given channel to a particular value (or from another
613 channel)
614 The currently defined presets are:
616 gray
618 grey
619 converts an RGBA image into a grayscale image with alpha chan‐
620 nel, or an RGB image into a grayscale image without an alpha
621 channel.
622 This weights the RGB channels at 22.2%, 70.7% and 7.1% respec‐
624 tively.
625 noalpha
627 removes the alpha channel from a 2 or 4 channel image. An
628 identity for other images.
629 red
631 channel0
632 extracts the first channel of the image into a single channel
633 image
634 green
636 channel1
637 extracts the second channel of the image into a single channel
638 image
639 blue
641 channel2
642 extracts the third channel of the image into a single channel
643 image
644 alpha
646 extracts the alpha channel of the image into a single channel
647 image.
648 If the image has 1 or 3 channels (assumed to be grayscale of
650 RGB) then the resulting image will be all white.
651 rgb converts a grayscale image to RGB, preserving the alpha channel
653 if any
654 addalpha
656 adds an alpha channel to a grayscale or RGB image. Preserves
657 an existing alpha channel for a 2 or 4 channel image.
658 For example, to convert an RGB image into a greyscale image:
660 $new = $img->convert(preset=>'grey'); # or gray
662 or to convert a grayscale image to an RGB image:
664 $new = $img->convert(preset=>'rgb');
666 The presets aren't necessary simple constants in the code, some are
668 generated based on the number of channels in the input image.
669 If you want to perform some other colour transformation, you can
671 use the 'matrix' parameter.
672 For each output pixel the following matrix multiplication is done:
674 ⎪ channel[0] ⎪ ⎪ $c00, ..., $c0k ⎪ ⎪ inchannel[0] ⎪
676 ⎪ ... ⎪ = ⎪ ... ⎪ x ⎪ ... ⎪
677 ⎪ channel[k] ⎪ ⎪ $ck0, ..., $ckk ⎪ ⎪ inchannel[k] ⎪
678 1
679 Where C<k = $img-E<gt>getchannels()-1>.
680 So if you want to swap the red and green channels on a 3 channel
682 image:
683 $new = $img->convert(matrix=>[ [ 0, 1, 0 ],
685 [ 1, 0, 0 ],
686 [ 0, 0, 1 ] ]);
687 or to convert a 3 channel image to greyscale using equal weight‐
689 ings:
690 $new = $img->convert(matrix=>[ [ 0.333, 0.333, 0.334 ] ])
692 Convert a 2 channel image (grayscale with alpha) to an RGBA image
694 with the grey converted to the specified RGB color:
695 # set (RGB) scaled on the grey scale portion and copy the alpha
697 # channel as is
698 my $colored = $gray->convert(matrix=>[ [ ($red/255), 0 ],
699 [ ($green/255), 0 ],
700 [ ($blue/255), 0 ],
701 [ 0, 1 ],
702 ]);
703 To convert a 3 channel image to a 4 channel image with a 50 percent
705 alpha channel:
706 my $withalpha = $rgb->convert(matrix =>[ [ 1, 0, 0, 0 ],
708 [ 0, 1, 0, 0 ],
709 [ 0, 0, 1, 0 ],
710 [ 0, 0, 0, 0.5 ],
711 ]);
712 Color Mappings
714 map You can use the map method to map the values of each channel of an
716 image independently using a list of lookup tables. It's important
717 to realize that the modification is made inplace. The function
718 simply returns the input image again or undef on failure.
719 Each channel is mapped independently through a lookup table with
721 256 entries. The elements in the table should not be less than 0
722 and not greater than 255. If they are out of the 0..255 range they
723 are clamped to the range. If a table does not contain 256 entries
724 it is silently ignored.
725 Single channels can mapped by specifying their name and the mapping
727 table. The channel names are "red", "green", "blue", "alpha".
728 @map = map { int( $_/2 } 0..255;
730 $img->map( red=>\@map );
731 It is also possible to specify a single map that is applied to all
733 channels, alpha channel included. For example this applies a gamma
734 correction with a gamma of 1.4 to the input image.
735 $gamma = 1.4;
737 @map = map { int( 0.5 + 255*($_/255)**$gamma ) } 0..255;
738 $img->map(all=> \@map);
739 The "all" map is used as a default channel, if no other map is
741 specified for a channel then the "all" map is used instead. If we
742 had not wanted to apply gamma to the alpha channel we would have
743 used:
744 $img->map(all=> \@map, alpha=>[]);
746 Since "[]" contains fewer than 256 element the gamma channel is
748 unaffected.
749 It is also possible to simply specify an array of maps that are
751 applied to the images in the rgba order. For example to apply maps
752 to the "red" and "blue" channels one would use:
753 $img->map(maps=>[\@redmap, [], \@bluemap]);
755
757 Imager, Imager::Engines
758
760 Tony Cook <tony@imager.perl.org>, Arnar M. Hrafnkelsson
761
763 $Revision: 1431 $
764perl v5.8.8 2008-03-28 Imager::Transformations(3)