Imagick::setResolution

(PECL imagick 2, PECL imagick 3)

Imagick::setResolution — Sets the image resolution

说明

public Imagick::setResolution ( float $x_resolution , float $y_resolution ) : bool

Sets the image resolution.

参数

x_resolution

The horizontal resolution.

y_resolution

The vertical resolution.

返回值

成功时返回 true。

注释

Imagick::setResolution() must be called before loading or creating an image.

参见

User Contributed Notes

carter dot sharon at gmail dot com 11-Oct-2010 11:07
If you are reading or creating a new image and want to set the resolution you need to set the Image Units. Undefined image units will cause imagick to use the default resolution (72x72).

<?php
$img = new Imagick();
   
$img->setResolution(300,300);
$img->newimage(100,100,'none');   
$img->setImageFormat('png');
// imagick::RESOLUTION_UNDEFINED  imagick::RESOLUTION_PIXELSPERINCH  imagick::RESOLUTION_PIXELSPERCENTIMETER

$img->setImageUnits(imagick::RESOLUTION_PIXELSPERINCH);

print_r($img->identifyImage());
   
?>

Output
Array (
[resolution] => Array ( [x] => 300 [y] => 300 )
[units] => PixelsPerInch
)
sualk at lednew dot de 07-Jan-2010 06:50
This method uses the "convert -density {$x_resolution}x{$y_resolution}" parameter. However be aware, that Imagick::setResolution() is much more alike the "convert -density" option than Imagick::setImageResolution()

It's very irritating that both Imagick::setResolution() and Imagick::setImageResolution() are introduced with "Sets the image resolution."

Use Imagick::setResolution() prior to reading a raster image. This method does not affect an image. However this method tells the image to which size it has to be sized in relation to images inherent resolution! With this method you are able to affect the real pixel-size of an image after reading. E.g. your image has a size of 100x100 pixels and an inherent resolution of 72. Setting the Resolution to 144 and reading this image results in a new image size of 200x200 pixels.

<?php
$im = new Imagick();
$im->setResolution(144,144);
$im->readImage("test.eps");
$im->setImageFormat("png");
header("Content-Type: image/png");
echo $im;
?>

Use Imagick::setImageResolution() to alter the resolution of an already read image. This method does not actually change the size of an image, but has influence to methods, which depends on a given image resolution like Imagick::resampleImage(). E.g. your image has a size of 100x100 pixels and a resolution of 72. Setting ImageResolution to 144 does nothing, unless you are resampling image afterwards in relation to the ImageResolution you set!

<?php
$im = new Imagick();
$im->readImage("test.eps");
$im->setImageResolution(144,144);
$im->resampleImage  (288,288,imagick::FILTER_UNDEFINED,1);
$im->setImageFormat("png");
header("Content-Type: image/png");
echo $im;
?>

which actually does the same like

<?php
$im = new Imagick();
$im->readImage("test.eps");
$im->setImageResolution(72,72);
$im->resampleImage  (144,144,imagick::FILTER_UNDEFINED,1);
$im->setImageFormat("png");
header("Content-Type: image/png");
echo $im;
?>