Hình ảnh php/png nền trong suốt

Examples

Compress uploaded PNG file

You can compress a PNG file when it's uploaded: (remember to change name in $_FILE[] và $save_to_path)

$read_from_path = $_FILE['file']['tmp_name'];
$save_to_path = "uploads/compressed_file.png";

$compressed_png_content = compress_png($read_from_path);
file_put_contents($save_to_path, $compressed_png_content);

// you don't need move_uploaded_file(). file_put_contents() will do that instead.

Chuyển đổi các tệp PNG một cách nhanh chóng

Bạn tối ưu hóa các tệp PNG đã có trên đĩa

$path_to_uncompressed_file = 'test.png';
$path_to_compressed_file = 'test-small.png';

// this will ensure that $path_to_compressed_file points to compressed file
// and avoid re-compressing if it's been done already
if (!file_exists($path_to_compressed_file)) {
    file_put_contents($path_to_compressed_file, compress_png($path_to_uncompressed_file));
}

// and now, for example, you can output the compressed file:
header("Content-Type: image/png");
header('Content-Length: '.filesize($path_to_compressed_file));
readfile($path_to_compressed_file);

Mã trên trang này là Miền công cộng. Hãy sao chép và làm bất cứ điều gì bạn thích

Trở về trang chủ

If you want to create a *transparent* PNG image, where the background is fully transparent, and all draw operations happen on-top of this, then do the following:

    $png = imagecreatetruecolor(800, 600);
    imagesavealpha($png, true);

________số 8_______

    $red = imagecolorallocate($png, 255, 0, 0);
    imagefilledellipse($png, 400, 300, 400, 300, $red);

    header("Content-type: image/png");
    imagepng($png);
?>

What you do is create a true colour image, make sure that the alpha save-state is on, then fill the image with a colour that has had its alpha level set to fully transparent (127).

The resulting PNG from the code above will have a red circle on a fully transparent background (drag the image into Photoshop to see for yourself)

i had problems with the example by sandhawk at spies dot com because my png overlay, and the jpeg canvas were using different color depths, so, this function corrects this:

[code]
function WatermarkImage($CanvasImage, $WatermarkImage /* MUST BE PHG */, $Opacity=10, $Quality=75)
{
    // create true color canvas image:
    $canvas_src = imagecreatefromjpeg($CanvasImage);
    $canvas_w = ImageSX($canvas_src);
    $canvas_h = ImageSY($canvas_src);
    $canvas_img = imagecreatetruecolor($canvas_w, $canvas_h);
    imagecopy($canvas_img, $canvas_src, 0,0,0,0, $canvas_w, $canvas_h);
    imagedestroy($canvas_src);    // no longer needed

    // create true color overlay image:
    $overlay_src = imagecreatefrompng($WatermarkImage);
    $overlay_w = ImageSX($overlay_src);
    $overlay_h = ImageSY($overlay_src);
    $overlay_img = imagecreatetruecolor($overlay_w, $overlay_h);
    imagecopy($overlay_img, $overlay_src, 0,0,0,0, $overlay_w, $overlay_h);
    imagedestroy($overlay_src);    // no longer needed

    // setup transparent color (pick one):
    $black   = imagecolorallocate($overlay_img, 0x00, 0x00, 0x00);
    $white   = imagecolorallocate($overlay_img, 0xFF, 0xFF, 0xFF);
    $magenta = imagecolorallocate($overlay_img, 0xFF, 0x00, 0xFF);
    // and use it here:
    imagecolortransparent($overlay_img, $white);

    // copy and merge the overlay image and the canvas image:
    imagecopymerge($canvas_img, $overlay_img, 0,0,0,0, $overlay_w, $overlay_h, $Opacity);

    // output:
    header("Content-type: image/jpeg");
    imagejpeg($canvas_img, '', $Quality);

    imagedestroy($overlay_img);
    imagedestroy($canvas_img);
}

// call function with opcity set to 50% and 95% quality
WatermarkImage("canvas.jpg", "overlay.png", 50, 95);

[/code]

If you want to resize a png-24 image and preserve the alpha channel you need to set imagealphablending($im_dest, false) on the destination image just after creating it with imagecreatetruecolor() and do a imagesavealpha($im_dest, true) on it before saving it:

$im = ImageCreateFromPNG('redfade.png');

$im_dest = imagecreatetruecolor (500, 300);
imagealphablending($im_dest, false);

imagecopyresampled($im_dest, $im, 0, 0, 0, 0, 300, 300, 500, 300);

imagesavealpha($im_dest, true);
imagepng($im_re, 'small_redfade.png');

?>