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imagecolorat (PHP 3, PHP 4, PHP 5) imagecolorat -- Get the index of the color of a pixel Descriptionint imagecolorat ( resource image, int x, int y )
Returns the index of the color of the pixel at the
specified location in the image specified by image.
If PHP is compiled against GD library 2.0 or higher and the image is a
truecolor image, this function returns the RGB value of that pixel as
integer. Use bitshifting and masking to access the distinct red, green and blue
component values:
Przykład 1. Access distinct RGB values |
<?php
$im = ImageCreateFromPng("rockym.png");
$rgb = ImageColorAt($im, 100, 100);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
?>
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See also imagecolorset() and
imagecolorsforindex().
User Contributed Notesrobert at future-vision dot nl
16-Dec-2005 01:53
Look mom, no tables :)
I made some changes to the code from 'hazard AT krankteil DOTTILLYDO de' so the function would output a div that displays the image.
As for the size of the outputted file I can say the original png file was lots smaller, but maybe its a nice feature for small buttons or such.
The way you can use it is the same as the code from 'hazard AT krankteil DOTTILLYDO de'.
litle note: each div contains a bogus image. When this is not in IE will screw up the output.
<?
function hexcolor($c) {
$r = ($c >> 16) & 0xFF;
$g = ($c >> 8) & 0xFF;
$b = $c & 0xFF;
return '#'.str_pad(dechex($r), 2, '0', STR_PAD_LEFT).str_pad(dechex($g), 2, '0', STR_PAD_LEFT).str_pad(dechex($b), 2, '0', STR_PAD_LEFT);
}
function png2div($filename) {
$img = imagecreatefrompng($filename);
$width = imagesx($img);
$height = imagesy($img);
$div_width = 1;
$previous_color = 0;
$output = '<div style="position:relative;width:' . $width . 'px;height:'. $height .'px;">';
for($y = 0;$y < $height;++$y){
for($x = 0;$x < $width;++$x){
$current_color = ImageColorAt($img, $x, $y);
if($current_color == $previous_color && $x < $width-1){
++$div_width;
}
else{
$output .= '<div style="position:relative;float:left;width:' . $div_width . 'px;height:1px;background-color:' . hexcolor((($div_width > 1)? $previous_color:$current_color)) . '"><img src="bogus.gif" alt="" width="1" height="1" /></div>';
$previous_color = $current_color;
$div_width = 1;
}
}
ob_flush();
}
$output .= '</div>';
return $output;
}
?>
hazard AT krankteil DOTTILLYDO de
12-Nov-2005 09:23
T. Dekker
27-Oct-2005 09:40
In GD 2.x there is support for true color images complete with an alpha channel. GD 2.x has a 7-bit (0-127) alpha channel.
While most people are used to an 8-bit (0-255) alpha channel, it is actually quite handy that GD's is 7-bit (0-127). Each pixel is represented by a 32-bit signed integer, with the four 8-bit bytes arranged like this:
High Byte <--> Low Byte
{Alpha Channel} {Red} {Green} {Blue}
For a signed integer, the leftmost bit, or the highest bit, is used to indicate whether the value is negative, thus leaving only 31 bits of actual information. PHP's default integer value is a signed long into which we can store a single GD palette entry. Whether that integer is positive or negative tells us whether antialiasing is enabled for that palette entry.
swimgod
02-Sep-2005 10:36
this function i made will compare two($start-$finish) images and change the pixels with diffrent colors in the "finish" image
then displays them both next to each other in one image
another feature is "display" which will echo text
"50% on
50% off"-% count(if the number is lower then 1 it will go into one decamil count
or type "2" will be
"10023 on
3000 off"-pixel count
one last feature is "color"
which you define in an array
$color = array("r" => "244","g" => "122","b" => "100");
to finish up the discrpition im gonna show this "map" of my function
compare($start, $finish[, $color[, $display[, $type]]])
image-url($start) - base image URL
image-url($finish) - compare image URL
array($color) - array with keys "r", "g", "b" r being RED 0-255 g being GREEN 0-255 b being BLUE 0-255
bool($display) - 1 OR TRUE will return text stats from compare
int($type) - 1 OR 0 | 1 being % results | 0 being pixel results
<?
function compare($start, $finish, $color, $display, $type){
$im = ImageCreateFrompng($start);
$im2 = ImageCreateFrompng($finish);
$img['x'] = imagesx($im);
$img['y'] = imagesy($im);
$img2['x'] = imagesx($im2);
$img2['y'] = imagesy($im2);
if(($img['x'] == $img2['x']) && ($img['y'] == $img2['y'])){
$i = array("width" => $img['x']*2, "height" => $img['y']);
$im3 = imagecreatetruecolor($i['width'], $i['height']);
if($color){
$color = imagecolorallocate($im3, $color['r'], $color['g'], $color['b']);
}else{
$color = imagecolorallocate($im3, 255, 255, 255);
}
for($y = $img['y'];$y > 0; $y--){
for($x = $img['x'];$x > 0; $x--){
if(ImageColorAt($im, $x, $y) == ImageColorAt($im2, $x, $y)){
$on = $on+1;
$rgb = ImageColorAt($im, $x, $y);
Imagesetpixel($im3, $img['x']+$x, $y, $rgb);
}else{
$off = $off+1;
imagesetpixel($im3, $img['x']+$x, $y , $color);
}
}
}
if($display == true){
if(($type == "1") || (!$type)){
$off2 = (round(($off / $on)*10));
if(($off2 == 0) && ($off > 0)){
$off2 = round(($off / $on)*10)*10;
}
$on2 = (100-$off2);
$off2 .="%";
$on2 .="%";
}else{
$off2 = $off;
$on2 = $on;
}
echo $off2 ." off<br>". $on2 ." on";
}else{
imagecopy($im3, $im, 0, 0, 0, 0, $img['x'], $img['y']);
@header("Content-type: image/png");
imagepng($im3);
imagedestroy($im3);
}
imagedestroy($im);
imagedestroy($im2);
return TRUE;
}else{
return False;
}
}
?>
Super Moi
28-Aug-2005 05:31
Here is a contribution for change tint.
function colorize($path_image, $red, $green, $blue)
{
$im = imagecreatefrompng($path_image);
$pixel = array();
$n_im = imagecreatetruecolor(imagesx($im),imagesy($im));
$fond = imagecolorallocatealpha($n_im, 255, 255, 255, 0);
imagefill($n_im, 0, 0, $fond);
for($y=0;$y<imagesy($n_im);$y++)
{
for($x=0;$x<imagesx($n_im);$x++)
{
$rgb = imagecolorat($im, $x, $y);
$pixel = imagecolorsforindex($im, $rgb);
$r = min(round($red*$pixel['red']/169),255);
$g = min(round($green*$pixel['green']/169),255);
$b = min(round($blue*$pixel['blue']/169),255);
$a = $pixel['alpha'];
//echo('red : '.$pixel['red'].' => '.$r.', green : '.$pixel['green'].' => '.$g.', blue : '.$pixel['blue'].' => '.$b.', alpha : '.$pixel['alpha'].' => '.$a.'<br>');
$pixelcolor = imagecolorallocatealpha($n_im, $r, $g, $b, $a);
imagealphablending($n_im, TRUE);
imagesetpixel($n_im, $x, $y, $pixelcolor);
}
}
imagepng($n_im,'test.png');
imagedestroy($n_im);
}
bpgordon at gmail dot com
23-May-2005 11:55
(the previous post was mistyped; please delete)
The following code converts a png image to an html table made up of colored 1x1 cells. Put the path (relative to the location of the script) to the image to be converted in the query, like this: http://yoursite.com/conv.php?image.png
Remember that you can only use a remote path if remote fopen is enabled.
<?php
print "<table border=0 cellpadding=0 cellspacing=0><tr>";
$image = imagecreatefrompng($_ENV["QUERY_STRING"]);
$xdim = imagesx($image);
$ydim = imagesy($image);
for ($x = 1; $x <= $xdim-1; $x++) {
for ($y = 1; $y <= $ydim-1; $y++) {
$rgb = imagecolorat($image, $x, $y);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
print "<td width=\"1\" height=\"1\" style=\"background-color: rgb($r, $g, $b);\"></td>";
}
print "</tr><tr>";
}
print "</tr></table>";
?>
bpgordon at gmail dot com
22-May-2005 07:19
The following code converts a png image to an html table made up of colored 1x1 cells. Put the path (relative to the location of the script) to the image to be converted in the query, like this: http://yoursite.com/conv.php?image.png
Remember that you can only use a remote path if remote fopen is enabled.
<?php
print "<table border=0 cellpadding=0 cellspacing=0><tr>";
$image = imagecreatefrompng($_ENV["QUERY_STRING"]);
$xdim = imagesx($image);
$ydim = imagesy($image);
for ($x = 1; $x <= $xdim-1; $x++) {
for ($y = 1; $y <= $ydim-1; $y++) {
$rgb = imagecolorat($image, $x, $y);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
print "<td width=\"1\" height=\"1\" style=\"background-color: rgb($r, $g, $b);\"></td>";
}
print "</tr><tr>";
}
print "</tr></table>";
?>
sys NO SPAM coder at gmail dot NOSPAM dot com
26-Apr-2005 12:40
Just for fun: another snippet for drawing images using html only X)
<html>
<head>
<style>
<!--
body {
font-family: courier new, courier;
font-size: 7pt;
background: #000000;
color: #000000;
}
-->
</style>
</head>
<body>
<font color="#000000">
<?php
$im = ImageCreateFromPng($_GET['img']);
$lastcolor=0;
for($y=0;$y<imagesy($im);$y++)
{
for($x=0;$x<imagesx($im);$x++)
{
$pixel = ImageColorAt($im, $x, $y);
if($lastcolor != $pixel)
{
printf('</font><font color="#%06x">', $pixel);
$lastcolor = $pixel;
}
echo "*";
}
echo "<br />";
}
?>
</font>
</body>
</html>
18-Jan-2005 11:08
Optimal:
<?php
$rgb = imagecolorat($im, $x, $y);
$r = ($rgb >> 16);
$g = ($rgb >> 8) & 255;
$b = $rgb & 255;
?>
As you see, you can also use decimal values (faster).
jed at jed dot bz
19-Oct-2004 11:14
In my various play stages with photomosaics I ended up writing this function that works with GD 2. The conversion from RGB to HSL is straightforward and there are a number of papers on it on our beloved Internet; however, this function simply finds the lightness value for a pixel and works exactly the same as imagecolorat().
<?php
function imagelightnessat($img, $x, $y)
{
if(!is_resource($img))
{
trigger_error("imagelightnessat(): supplied argument is not a valid "
. "Image resource", E_USER_WARNING);
return 0.0;
}
$c = @imagecolorat($img, $x, $y);
if($c === false) return false;
if(imageistruecolor($img))
{
$red = ($c >> 16) & 0xFF;
$green = ($c >> 8) & 0xFF;
$blue = $c & 0xFF;
}
else
{
$i = imagecolorsforindex($img, $c);
$red = $i['red'];
$green = $i['green'];
$blue = $i['blue'];
}
$m = min($red, $green, $blue);
$n = max($red, $green, $blue);
$lightness = (double)(($m + $n) / 510.0);
return($lightness);
}
?>
mumig at poczta dot onet dot pl
27-Feb-2004 05:13
imagecolorat() works differently for png's with true color and for paletted png's - for true color it returns value of color, for paletted it returns index number and you have to use imagecolorsforindex() to get rgb color value.
geat AT zoom DOT co DOT uk
10-Jun-2003 01:35
The HTML image renderer didn't work for me for some reason, but here's a version that does...
echo '<table border="0" cellspacing="0" cellpadding="0">';
$im = ImageCreateFromJPEG("IMAGE NAME");
$width = imagesx($im);
$height = imagesy($im);
for ($cy=0;$cy<$height;$cy++) {
echo '<tr>';
for ($cx=0;$cx<$width;$cx++) {
$rgb = ImageColorAt($im, $cx, $cy);
$col = imagecolorsforindex($im, $rgb);
printf('<td width="2" height="2" bgcolor=#%02x%02x%02x></td>', $col["red"], $col["green"], $col["blue"]);
}
echo '</tr>';
}
echo '</table>';
28-May-2003 05:54
Just for fun, here is a little snippet that "paints" a image in html only. Try it out with very small images, as this is a real browser-killer. mozilla > 120mb ram, ie > 100mb with a 300x200 image :-)
$file = "image.png";
$im = imagecreatefrompng($file);
$size_arr = getimagesize($file);
echo "<table width=".$size_arr[0]." height=".$size_arr[1]." cellpadding=0 cellspacing=0 border=0>";
for ($y=0; $y<$size_arr[1]; $y++) {
echo "<tr>";
for ($x=0; $x<$size_arr[0]; $x++) {
$rgb = ImageColorAt($im, $x, $y);
printf("<td width=1 bgcolor=%06x><img width=1></td>", $rgb);
}
echo "</tr>";
}
echo "</table>";
lachy at kennedia dot com
21-Jan-2003 03:25
It seems that if you don not have GD 2.0.1+ then the alpha value will not be available.
ceresATdivxmaniaDOTit
03-Jan-2003 12:46
To get RGB values of a pixel in a truecolor image:
<?
$image=imageCreateFromJPEG('image.jpg');
$x = 10;
$y = 15;
$colorindex = imagecolorat($image,$x,$y);
$colorrgb = imagecolorsforindex($image,$colorindex);
echo "RGB values of the pixel at position $x - $y are: $colorrgb['red'] $colorrgb['green'] $colorrgb['blue'] \n Apha value is: $colorrgb['alpha']";
?>
pete at spamisbad_holidian dot com
05-Jul-2002 09:36
If you have a truecolor image and absolutely need to get the actual color of a pixel, it seems like you could create a 16x16 indexed color image from a part of the True Color image containing the pixel(s) in question. Then you should be able to guarantee that the indexed sample has the indentical colors to the True Color image. you can then use this function to get the color index of a pixel in the sample.
Obviously, this would be an intensive way to get pixel colors, especially for a large image, but as far as I can tell, it's one of the very few ways to do it right now.
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