我需要将PNG图片(https://chart.googleapis.com/chart?cht=lxy&chd=e:AACIERGZIiKqMzO7RETMVVXdZmbud3f.iIkQmZohqqsyu7xDzM1U3d5l7u92,hhiIivfFmZZmcCY.YYZmTgdQjWd3kk6g880asfu7r4sf4E22tGtGsfzzmZj9&chds=0.0,1.0&chs=105x75&chma=1,0,1,1&chco=42b6c9ff&chls=2.5,1.0,0.0&chxl=0:%7C%7C1:%7C%7C2:%7C)的背景颜色更改为透明。我使用下面的代码，我觉得是对的:
$picture = imagecreatefrompng("https://chart.googleapis.com/chart?cht=lxy&chd=e:AACIERGZIiKqMzO7RETMVVXdZmbud3f.iIkQmZohqqsyu7xDzM1U3d5l7u92,hhiIivfFmZZmcCY.YYZmTgdQjWd3kk6g880asfu7r4sf4E22tGtGsfzzmZj9&chds=0.0,1.0&chs=105x75&chma=1,0,1,1&chco=42b6c9ff&chls=2.5,1.0,0.0&chxl=0:%7C%7C1:%7C%7C2:%7C");
$img_w = imagesx($picture);
$img_h = imagesy($picture);
imagealphablending($picture, false);
imagesavealpha($picture, true);
$rgb = imagecolorexact ($picture, 255,255,255);//imagecolorat($picture, 50, 50);
imagecolortransparent($picture, $rgb);
imagepng($picture, '../images/chart2.png');
imagedestroy($picture);
我用imagecolorat太检测准确的颜色，但结果是一样的-它不工作(背景是白色的(不透明))!我错在哪里?
可能重复:PHP:如何使一个绿色的区域(背景)在一个图像透明?和
我已经解决了这个问题:
<?
$picture = imagecreatefrompng("../images/chart.png");
$img_w = imagesx($picture);
$img_h = imagesy($picture);
$newPicture = imagecreatetruecolor( $img_w, $img_h );
imagesavealpha( $newPicture, true );
$rgb = imagecolorallocatealpha( $newPicture, 0, 0, 0, 127 );
imagefill( $newPicture, 0, 0, $rgb );
$color = imagecolorat( $picture, $img_w-1, 1);
for( $x = 0; $x < $img_w; $x++ ) {
for( $y = 0; $y < $img_h; $y++ ) {
$c = imagecolorat( $picture, $x, $y );
if($color!=$c){
imagesetpixel( $newPicture, $x, $y, $c);
}
}
}
imagepng($newPicture, '../images/chart2.png');
imagedestroy($newPicture);
imagedestroy($picture);
我希望它能帮助到别人。
<?php
$img = imagecreatefrompng("https://i.stack.imgur.com/4NoTj.png"); //image obj from url
$bg_color = imagecolorat($img,1,1); //get color of top-left pixel
imagecolortransparent($img, $bg_color); //matching px => transparent
imagepng($img); //output png
imagedestroy($img); //cleanup
?>
文档:imagecolortransparent, imagepng