PHP implements a method for zooming a PNG image (supports transparent backgrounds)

The example in this paper describes how PHP implements scaling of PNG images. Share to everyone for your reference. The implementation method is as follows: function Smart_resize_image ($file, $width = 0, $height = 0, $proportional = false, $output = ' file ', $delete _original = t Rue, $use _linux_commands = False) { if ($height <= 0 && $width <= 0) { return false; } $info = getimagesize ($file); $image = "; $final _width = 0; $final _height = 0; List ($width _old, $height _old) = $info; if ($proportional) { if ($width = = 0) $factor = $height/$height _old; ElseIf ($height = = 0) $factor = $width/$width _old; else $factor = min ($width/$width _old, $height/$height _old); $final _width = Round ($width _old * $factor); $final _height = Round ($height _old * $factor); } else { $final _width = ($width <= 0)? $width _old: $width; $final _height = ($height <= 0)? $height _old: $height; } Switch ($info [2]) { Case Imagetype_gif: $image = Imagecreatefromgif ($file); Break Case IMAGETYPE_JPEG: $image = Imagecreatefromjpeg ($file); Break Case Imagetype_png: $image = Imagecreatefrompng ($file); Break Default return false; } $image _resized = Imagecreatetruecolor ($final _width, $final _height); if (($info [2] = = Imagetype_gif) | | ($info [2] = = Imagetype_png)) { $trnprt _indx = imagecolortransparent ($image); If we have a specific transparent color if ($trnprt _indx >= 0) { Get the original image ' s transparent color ' s RGB values $trnprt _color = Imagecolorsforindex ($image, $trnprt _indx); Allocate the same color in the new image resource $trnprt _indx = imagecolorallocate ($image _resized, $trnprt _color[' Red '], $trnprt _color[' green ', $trnprt _color[' Blue ']); Completely fill the background of the new image with allocated color. Imagefill ($image _resized, 0, 0, $trnprt _indx); Set the background color for new image to Transparent Imagecolortransparent ($image _resized, $trnprt _indx); } Always make a transparent background color for PNGs that don ' t has one allocated already ElseIf ($info [2] = = Imagetype_png) { Turn off transparency Blending (temporarily) Imagealphablending ($image _resized, false); Create a new transparent color for image $color = Imagecolorallocatealpha ($image _resized, 0, 0, 0, 127); Completely fill the background of the new image with allocated color. Imagefill ($image _resized, 0, 0, $color); Restore Transparency Blending Imagesavealpha ($image _resized, true); } } Imagecopyresampled ($image _resized, $image, 0, 0, 0, 0, $final _width, $final _height, $width _old, $height _old); if ($delete _original) { if ($use _linux_commands) EXEC (' rm '. $file); Else @unlink ($file); } Switch (Strtolower ($output)) { Case ' Browser ': $mime = Image_type_to_mime_type ($info [2]); Header ("Content-type: $mime"); $output = NULL; Break Case ' file ': $output = $file; Break Case ' return ': return $image _resized; Break Default Break } Switch ($info [2]) { Case Imagetype_gif: Imagegif ($image _resized, $output); Break Case IMAGETYPE_JPEG: Imagejpeg ($image _resized, $output); Break Case Imagetype_png: Imagepng ($image _resized, $output); Break Default return false; } return true; } Copy Code I hope this article is helpful to everyone's PHP programming.

PHP, PNG

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