imagesetinterpolation

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

imagesetinterpolation — Set the interpolation method

Description

imagesetinterpolation(GdImage $image, int $method = IMG_BILINEAR_FIXED): bool

Sets the interpolation method, setting an interpolation method affects the rendering of various functions in GD, such as the imagerotate() function.

Parameters

image

A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor().

method

The interpolation method, which can be one of the following:

IMG_BELL: Bell filter.
IMG_BESSEL: Bessel filter.
IMG_BICUBIC: Bicubic interpolation.
IMG_BICUBIC_FIXED: Fixed point implementation of the bicubic interpolation.
IMG_BILINEAR_FIXED: Fixed point implementation of the bilinear interpolation (default (also on image creation)).
IMG_BLACKMAN: Blackman window function.
IMG_BOX: Box blur filter.
IMG_BSPLINE: Spline interpolation.
IMG_CATMULLROM: Cubic Hermite spline interpolation.
IMG_GAUSSIAN: Gaussian function.
IMG_GENERALIZED_CUBIC: Generalized cubic spline fractal interpolation.
IMG_HERMITE: Hermite interpolation.
IMG_HAMMING: Hamming filter.
IMG_HANNING: Hanning filter.
IMG_MITCHELL: Mitchell filter.
IMG_POWER: Power interpolation.
IMG_QUADRATIC: Inverse quadratic interpolation.
IMG_SINC: Sinc function.
IMG_NEAREST_NEIGHBOUR: Nearest neighbour interpolation.
IMG_WEIGHTED4: Weighting filter.
IMG_TRIANGLE: Triangle interpolation.

Return Values

Returns true on success or false on failure.

Changelog

Version	Description
8.0.0	`image` expects a GdImage instance now; previously, a valid `gd` resource was expected.

Examples

Example #1 imagesetinterpolation() example

<?php
// Load an image
$im = imagecreate(500, 500);

// By default interpolation is IMG_BILINEAR_FIXED, switch 
// to use the 'Mitchell' filter:
imagesetinterpolation($im, IMG_MITCHELL);

// Continue to work with $im ...
?>

Notes

Changing the interpolation method affects the following functions when rendering:

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User Contributed Notes 1 note

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-1

shaun at slickdesign dot com dot au ¶

7 years ago

Setting the interpolation does not carry through to any images created by imageaffine() or imagerotate(). It defaults to IMG_BILINEAR_FIXED and would need to be set on each generated image as required.

<?php
imagesetinterpolation( $image, IMG_NEAREST_NEIGHBOUR );

// Rotated using IMG_NEAREST_NEIGHBOUR
$rotated = imagerotate( $image, 45, $transparent );

// Rotated using IMG_BILINEAR_FIXED
$rotated_again = imagerotate( $rotated, 45, $transparent );
?>

Setting the interpolation to IMG_NEAREST_NEIGHBOUR can help to preserve details and prevent sampling issues when rotating an image at 90 degree increments, including when rotating clockwise.

<?php
// Rotated image can appear blurred and on a slight angle.
$rotated = imagerotate( $image, -360, $transparent );

// Similar to starting Image although it may still show a background or be on a slight angle.
imagesetinterpolation( $image, IMG_NEAREST_NEIGHBOUR );
$rotated = imagerotate( $image, -360, $transparent );
?>