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php image resample 이미지 크기변경 화질

  • 참고링크 : https://stackoverflow.com/questions/3617272/php-gd-bad-quality-on-resize

imagesetinterpolation

  • https://www.php.net/manual/en/function.imagesetinterpolation.php
  • 다운샘플링 의 경우 IMG_SINC 알고리즘을 사용하는 것이 더 선명한 결과를 제공하는 경향이 있습니다.
  • 업샘플링의 경우 IMG_BICUBIC_FIXED, IMG_GENERALIZED_CUBIC 및 IMG_QUADRATIC이 더 나은 결과를 제공할 수 있습니다.

imagecopyresampled

  • https://www.php.net/manual/en/function.imagecopyresampled.php

interpolation 보간

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.

사용법

	$dimg = imagecreatetruecolor($nw, $nh);
	//imagesetinterpolation($dimg, IMG_SINC);
	imagesetinterpolation($dimg, IMG_BILINEAR_FIXED);
  • 이미지 생성 이후에 샘플링 방법을 명시하면됨