Grayscaling images causes mangled image + segfault

[comp.lang.php]

[php]
/**
* Class for grayscaling image
*
* @author Phil Powell
* @version 1.2.1
* @package IMAGE_CATALOG:: IMAGE
*/
class ImageGrayscaleG enerator extends ImageResizeComp onents {

/
*----------------------------------------------------------------------------------------------------------------------------------------------------------
This class exists due to the rather poor performance of the
imagecopymergeg ray() command
Borrowing code snippet from http://us3.php.net/manual/en/functio...ymergegray.php
first line comment
Will perform actual grayscaling of image one pixel at a time.
-----------------------------------------------------------------------------------------------------------------------------------------------------------
*/
// REMEMBER TO USE REFERENCE POINTER ONTO $image OBJECT TO ENSURE
"static" CHANGE TO OBJECT AND NOT TO INSTANCE

/**
* Constructor. Set all properties dynamically
*
* @access public
* @param resource $image (reference)
* @param resource $newImage (reference)
* @param int $image_width
* @param int $image_height
*/
function ImageGrayscaleG enerator(&$imag e, &$newImage, $image_width,
$image_height) { // CONSTRUCTOR
global $section;
foreach (array($section , 'newImage', "${section}_wid th", "$
{section}_heigh t") as $val) $this->$val =& ${$val};
}

/**
* Make the image grayscale
*
* @access protected
*/
function makeGray() { // VOID METHOD
global $section;
for ($i = 0; $i <= 255; $i++) $colorNDX[$i] =
@imagecolorallo cate($this->newImage, $i, $i, $i);

if (is_array($colo rNDX) && @sizeof($colorN DX) 0) {
for ($y = 0; $y < $this->{$section . '_height'}; $y++) {
for ($x = 0; $x < $this->{$section . '_width'}; $x++) {
$ndx = @imagecolorat($ this->image, $x, $y);
$ndxColorArray = @imagecolorsfor index($this->image, $ndx);
$avg = floor(($ndxColo rArray['red'] + $ndxColorArray['green'] +
$ndxColorArray['blue']) / 3);
@imagesetpixel( $this->newImage, $x, $y, $colorNDX[$avg]);
}
}
}
}
}

if ($this->isSuccessful && $image && $willGrayscale) { // GRAYSCALE
IMAGE
$igg =& new ImageGrayscaleG enerator($image , $newImage,
$image_width, $image_height);
$igg->makeGray();
$igg = null;
}
[/php]

Whenever I run this class to grayscale an image, I wind up with the
resulting image being horribly mangled to the point of its original
format completely irreparable, furthermore, I wind up with an Apache
segfault and having to reboot the server to correct the problem.

Um, why?

Phil

[Jerry Stuckle]

comp.lang.php wrote:
<snip>

Thank you, Jerry, very nice to hear this! Unfortunately no I never
did solve the problem; I am still not capable of grayscaling an image:

/**
* Make the image grayscale
*
* @access protected
*/
function makeGray() { // VOID METHOD
global $section;
for ($i = 0; $i <= 255; $i++) $colorNDX[$i] =
@imagecolorallo cate($this->$section, $i, $i, $i);

for ($y = 0; $y < $this->{$section . '_height'}; $y++) {
for ($x = 0; $x < $this->{$section . '_width'}; $x++) {
$ndx = @imagecolorat($ this->$section, $x, $y);
$red = ($ndx >16) & 0xFF;
$green = ($ndx >8) & 0xFF;
$blue = $ndx & 0xFF;
//$ndxColorArray = @imagecolorsfor index($this->$section, $ndx);
//$avg = floor(($ndxColo rArray['red'] + $ndxColorArray['green'] +
$ndxColorArray['blue']) / 3);
$col = $red * 0.299 + $green * 0.587 + $blue * 0.114;
@imagesetpixel( $this->$section, $x, $y, $colorNDX[$col]);
}
}

//@imagecopy($thi s->newImage, $this->$section, 0, 0, 0, 0,
// $this->{$section . '_width'}, $this->{$section .
'_height'});

}

No image is ever produced in spite of the code produced.

>For your next post try alt.anal.orific es. It matches you perfectly.

--
============== ====
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstuck...@attg lobal.net
============== ====

I'm sorry, I thought you found a fix for it.

I looked at the code, but unfortunately I'm that great with the image
functions.

A couple of things I do see. First of all, you shouldn't use a global
($section). Anything you need you should pass to the function or the
class itself.

Also, in your constructor you're saving things in $this->$val, which is
incorrect in two counts. It should be $this->val, and you never defined
$val in your class. No idea what the code would do in this case.

And I'm not sure just what you're trying to accomplish in the foreach()
loop in your constructor. If you're trying to use this to create
variables in your class, that's the hard way to go about it, and the
values you're defining are temporary and will disappear at the end of
the function. Rather, you should just define them as members of the
class (probably private).

Also, I'm not sure what's in $section, but I think you're trying to get
the width and height of the image.

As for your makeGray() function -

You should first define $colorNDX as an array, i.e.

$colorNDX = array();

Your if statement following the for loop is unnecessary - you already
know it's an array of 256 elements because you just created it. And the
following nested for statements are referencing variables which don't
exist any more.

These are just off the top of my head, and may not be correct. But I
did find our class to be pretty hard to understand.

--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attgl obal.net
=============== ===

[Steve]

| Also, in your constructor you're saving things in $this->$val, which is
| incorrect in two counts. It should be $this->val, and you never defined
| $val in your class. No idea what the code would do in this case.

as i pointed out, it seems an attempt to dynamically create the class
interface names. nothing else makes sense.

| And I'm not sure just what you're trying to accomplish in the foreach()
| loop in your constructor. If you're trying to use this to create
| variables in your class, that's the hard way to go about it, and the
| values you're defining are temporary and will disappear at the end of
| the function. Rather, you should just define them as members of the
| class (probably private).

hmmm...sounds familiar. :)

| Also, I'm not sure what's in $section, but I think you're trying to get
| the width and height of the image.

so we agree that global $section is magic. i suppose you didn't read my
initial response.

| As for your makeGray() function -
|
| You should first define $colorNDX as an array, i.e.
|
| $colorNDX = array();

that only matters if he's displaying notices. otherwise he is dynamically
filling $colorNDX as an array type with allocated colors - he just doesn't
check to see if the color has *already* been allocated and does this in a
loop. but then again, i already pointed out these two flaws.

| Your if statement following the for loop is unnecessary - you already
| know it's an array of 256 elements because you just created it. And the
| following nested for statements are referencing variables which don't
| exist any more.

another reason why i said the author was 'brain-dead' thinking that this
version of code has better performance potential than the built-in php
function he was aiming to supplant!

| These are just off the top of my head, and may not be correct. But I
| did find our class to be pretty hard to understand.

so jerry, you found that my initial response to phil did not add anything to
the post. i find that interesting since you restated exactly 3 things there
i've already covered. and, off-the-top-of-MY-head i stated even more
potential problems with the op's eye-sore coding.

if it's the language i used that was offensive to you, then damn the
language...else , why nullify your opinion by restating what i've already
said!

as it is jerry, i did not know the op was in fact the author of this class.
perhaps i would have been more gentil and guarded with my flurry of insults
had i known before hand. i just find it hard for you to agree that i've not
added anything to resolving the problem at hand when you are mirroring my
findings...simp ly because you don't like the tone of my delivery.

oh well.

later.

[Jerry Stuckle]

Steve wrote:
<snip garbage>

I found your tone to be arrogant and condescending, whether he was the
author of the class or not.

And as I said before - alt.anal.orific es is thataway ===>
--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attgl obal.net
=============== ===

[Steve]

"Jerry Stuckle" <js*******@attg lobal.netwrote in message
news:sd******** *************** *******@comcast .com...
| Steve wrote:
| <snip garbage>
|
| I found your tone to be arrogant and condescending, whether he was the
| author of the class or not.
|
| And as I said before - alt.anal.orific es is thataway ===>

i couldn't care less how you find my tone. you have no response to justify
'i have to agree with...added nothing to...' whilst you're almost
word-for-wording my review of the code...other than, i didn't like your
tone. i can then duely note that you are fully qualified to tell me
directions to alt.anal.orific es since your head is apparently buried up
yours.

[Steve]

| And as I said before - alt.anal.orific es is thataway ===>

btw, since that's where your cranium resides, do i take this as an
invitation to come over and visit?

[asdf]

"Steve" <no****@example .comwrote in message
news:1k******** ******@newsfe02 .lga...

>
"comp.lang. php" <ph************ **@gmail.comwro te in message
news:11******** *************@l 77g2000hsb.goog legroups.com...
| On Apr 16, 1:47 am, "Steve" <no....@example .comwrote:
| "Steve" <no....@example .comwrote in message
| >
| news:m_******** *******@newsfe0 2.lga...
| | hey genious, here's an RBI:
| |
| | foreach (
| | array(
| | $section ,
| | 'newImage' ,
| | "${section}_wid th" ,
| | "${section}_hei ght"
| | )
| | as $val
| | ){ $this->$val =& ${$val}; }
| |
| | what do you intend to do with this lil' gem, eh? you do realize
you'll
get
| | the same results by just:
| |
| | $this->val =& "${section}_hei ght";
| >
| make that:
| >
| $this->$val =& ${"${section}_h eight"};
| >
| but you get my point. if you want to make the values into variables,
do
| it...but don't confuse the issue of what $this->$val is. this is right
up
| there with magic numbers! gotta love coders like you. ;^)
|
| Coders like me can spell "genius".

double-entandre dimwit

[snip]

Methinks you mean "double-entendre" (sp. again - ROFL)

[comp.lang.php]

On Apr 16, 4:37 pm, Jerry Stuckle <jstuck...@attg lobal.netwrote:

Steve wrote:

<snip garbage>

I found your tone to be arrogant and condescending, whether he was the
author of the class or not.

And as I said before - alt.anal.orific es is thataway ===>

Thanx Jerry for your help! Turns out that the simple process of having
class properties that I forgot to include fixed everything (*ahem*)

Phil

>
--
=============== ===
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstuck...@attgl obal.net
=============== ===

[Steve]

"comp.lang. php" <ph************ **@gmail.comwro te in message
news:11******** *************@y 80g2000hsf.goog legroups.com...
| On Apr 16, 4:37 pm, Jerry Stuckle <jstuck...@attg lobal.netwrote:
| Steve wrote:
| >
| <snip garbage>
| >
| I found your tone to be arrogant and condescending, whether he was the
| author of the class or not.
| >
| And as I said before - alt.anal.orific es is thataway ===>
|
| Thanx Jerry for your help! Turns out that the simple process of having
| class properties that I forgot to include fixed everything (*ahem*)

now on to fix the other problems noted, right? of course not. have you
benchmarked your performance against imagecopygraysc ale? of course not. will
you? probably. will you post the dire results back here...of course not.

keep slinging that code phil.

[comp.lang.php]

On Apr 17, 1:26 am, "Steve" <no....@example .comwrote:

"comp.lang. php" <phillip.s.pow. [e-mail] te in message

news:11******** *************@y 80g2000hsf.goog legroups.com...
| On Apr 16, 4:37 pm, Jerry Stuckle <jstuck...@attg lobal.netwrote: | Steve wrote:

| >
| <snip garbage>
| >
| I found your tone to be arrogant and condescending, whether he was the
| author of the class or not.
| >
| And as I said before - alt.anal.orific es is thataway ===>
|
| Thanx Jerry for your help! Turns out that the simple process of having
| class properties that I forgot to include fixed everything (*ahem*)

now on to fix the other problems noted, right? of course not. have you
benchmarked your performance against imagecopygraysc ale? of course not. will
you? probably. will you post the dire results back here...of course not.

keep slinging that code phil.

Thanx, I will! And I appreciate all of your help!

[Steve]

"comp.lang. php" <ph************ **@gmail.comwro te in message
news:11******** **************@ n59g2000hsh.goo glegroups.com.. .
| On Apr 17, 1:26 am, "Steve" <no....@example .comwrote:
| "comp.lang. php" <phillip.s.pow. [e-mail] te in message
| >
| news:11******** *************@y 80g2000hsf.goog legroups.com...
| | On Apr 16, 4:37 pm, Jerry Stuckle <jstuck...@attg lobal.netwrote: | >
Steve wrote:
| >
| | >
| | <snip garbage>
| | >
| | I found your tone to be arrogant and condescending, whether he was
the
| | author of the class or not.
| | >
| | And as I said before - alt.anal.orific es is thataway ===>
| |
| | Thanx Jerry for your help! Turns out that the simple process of having
| | class properties that I forgot to include fixed everything (*ahem*)
| >
| now on to fix the other problems noted, right? of course not. have you
| benchmarked your performance against imagecopygraysc ale? of course not.
will
| you? probably. will you post the dire results back here...of course not.
| >
| keep slinging that code phil.
|
| Thanx, I will! And I appreciate all of your help!

hey, no problem. you are single-handedly increasing my paygrade. companies
that have a go with you and those of your prowess soon learn that quality
has a much higher price tag. so, i thank you very much. :)