Efficiently resize the current image
Description
This is a WordPress specific implementation of Imagick::thumbnailImage(), which resizes an image to given dimensions and removes any associated profiles.
Parameters
$dst_w
intrequired- The destination width.
$dst_h
intrequired- The destination height.
$filter_name
stringoptional- The Imagick filter to use when resizing. Default
'FILTER_TRIANGLE'
.Default:
'FILTER_TRIANGLE'
$strip_meta
booloptional- Strip all profiles, excluding color profiles, from the image.
Default:
true
Source
protected function thumbnail_image( $dst_w, $dst_h, $filter_name = 'FILTER_TRIANGLE', $strip_meta = true ) {
$allowed_filters = array(
'FILTER_POINT',
'FILTER_BOX',
'FILTER_TRIANGLE',
'FILTER_HERMITE',
'FILTER_HANNING',
'FILTER_HAMMING',
'FILTER_BLACKMAN',
'FILTER_GAUSSIAN',
'FILTER_QUADRATIC',
'FILTER_CUBIC',
'FILTER_CATROM',
'FILTER_MITCHELL',
'FILTER_LANCZOS',
'FILTER_BESSEL',
'FILTER_SINC',
);
/**
* Set the filter value if '$filter_name' name is in the allowed list and the related
* Imagick constant is defined or fall back to the default filter.
*/
if ( in_array( $filter_name, $allowed_filters, true ) && defined( 'Imagick::' . $filter_name ) ) {
$filter = constant( 'Imagick::' . $filter_name );
} else {
$filter = defined( 'Imagick::FILTER_TRIANGLE' ) ? Imagick::FILTER_TRIANGLE : false;
}
/**
* Filters whether to strip metadata from images when they're resized.
*
* This filter only applies when resizing using the Imagick editor since GD
* always strips profiles by default.
*
* @since 4.5.0
*
* @param bool $strip_meta Whether to strip image metadata during resizing. Default true.
*/
if ( apply_filters( 'image_strip_meta', $strip_meta ) ) {
$this->strip_meta(); // Fail silently if not supported.
}
try {
/*
* To be more efficient, resample large images to 5x the destination size before resizing
* whenever the output size is less that 1/3 of the original image size (1/3^2 ~= .111),
* unless we would be resampling to a scale smaller than 128x128.
*/
if ( is_callable( array( $this->image, 'sampleImage' ) ) ) {
$resize_ratio = ( $dst_w / $this->size['width'] ) * ( $dst_h / $this->size['height'] );
$sample_factor = 5;
if ( $resize_ratio < .111 && ( $dst_w * $sample_factor > 128 && $dst_h * $sample_factor > 128 ) ) {
$this->image->sampleImage( $dst_w * $sample_factor, $dst_h * $sample_factor );
}
}
/*
* Use resizeImage() when it's available and a valid filter value is set.
* Otherwise, fall back to the scaleImage() method for resizing, which
* results in better image quality over resizeImage() with default filter
* settings and retains backward compatibility with pre 4.5 functionality.
*/
if ( is_callable( array( $this->image, 'resizeImage' ) ) && $filter ) {
$this->image->setOption( 'filter:support', '2.0' );
$this->image->resizeImage( $dst_w, $dst_h, $filter, 1 );
} else {
$this->image->scaleImage( $dst_w, $dst_h );
}
// Set appropriate quality settings after resizing.
if ( 'image/jpeg' === $this->mime_type ) {
if ( is_callable( array( $this->image, 'unsharpMaskImage' ) ) ) {
$this->image->unsharpMaskImage( 0.25, 0.25, 8, 0.065 );
}
$this->image->setOption( 'jpeg:fancy-upsampling', 'off' );
}
if ( 'image/png' === $this->mime_type ) {
$this->image->setOption( 'png:compression-filter', '5' );
$this->image->setOption( 'png:compression-level', '9' );
$this->image->setOption( 'png:compression-strategy', '1' );
$this->image->setOption( 'png:exclude-chunk', 'all' );
}
/*
* If alpha channel is not defined, set it opaque.
*
* Note that Imagick::getImageAlphaChannel() is only available if Imagick
* has been compiled against ImageMagick version 6.4.0 or newer.
*/
if ( is_callable( array( $this->image, 'getImageAlphaChannel' ) )
&& is_callable( array( $this->image, 'setImageAlphaChannel' ) )
&& defined( 'Imagick::ALPHACHANNEL_UNDEFINED' )
&& defined( 'Imagick::ALPHACHANNEL_OPAQUE' )
) {
if ( $this->image->getImageAlphaChannel() === Imagick::ALPHACHANNEL_UNDEFINED ) {
$this->image->setImageAlphaChannel( Imagick::ALPHACHANNEL_OPAQUE );
}
}
// Limit the bit depth of resized images to 8 bits per channel.
if ( is_callable( array( $this->image, 'getImageDepth' ) ) && is_callable( array( $this->image, 'setImageDepth' ) ) ) {
if ( 8 < $this->image->getImageDepth() ) {
$this->image->setImageDepth( 8 );
}
}
} catch ( Exception $e ) {
return new WP_Error( 'image_resize_error', $e->getMessage() );
}
}
Hooks
- apply_filters( ‘image_strip_meta’,
bool $strip_meta ) Filters whether to strip metadata from images when they’re resized.
Changelog
Version | Description |
---|---|
4.5.0 | Introduced. |
User Contributed Notes
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