PHP-将背景颜色更改为透明

问题描述

我需要PNG图象的改变背景颜色()透明.我使用下面的代码对我来说似乎正确:

I need to change background color of PNG picture (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) to transparent. I use the following code which seems to me right:

$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);

我也使用imagecolorat来检测准确的颜色，但是结果是相同的-它不起作用(背景是白色(不透明))！我怎么了?

I used imagecolorat too to detect accurate color, but the result is the same - it doesn't work(the background is white(not transparent))! What is my mistake?

可能的重复项: PHP:如何使图像中的绿色区域(背景)透明?和在PHP中 imagecolortransparent

Possible duplicates: PHP: How to make a green area (background) in an image transparent?andimagecolortransparent in PHP not working

推荐答案

我已经解决了这个问题:

I have solved this issue:

<?
$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);

我希望它可以帮助其他人.

I hope it helps someone else.

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