Grayscaling Image with GD causes image to turn jet black!

[Phil Powell]

I borrowed this code from a source:

for($a=0;$a<imagecolorstotal ($image_id);$a++)
{
$color = imageColorsForIndex($image_id,$i);
$R=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$G=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$B=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
imageColorSet($image_id, $a, $R, $G, $B);
}

using an image (in this case I'm using a JPEG) that is a true color
image I was unable to successfully use imagecopymergegray since that
washed out my hues/saturation altogether making the image illegible
(imagecopymergegray + imagecreate); otherwise, the colors overrode
imagecopymergegray (imagecopymergegray + imagecreatetruecolor).

Using the code I borrowed I was able to change the image.. except that
it turned jet black instead!

Has anyone ever successfully grayscaled an image using GD library? If
so, how did you do it?

Thanx
Phil

[CountScubula]

Try running an average of the three colors:
$avg = floor( ( $color['red']) + $color['green']) + $color['blue']) ) / 3 )
$R= $avg; $B = $avg; $G = $avg;
imageColorSet($image_id, $a, $R, $G, $B);
--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c*************************@posting.google.co m...

I borrowed this code from a source:

for($a=0;$a<imagecolorstotal ($image_id);$a++)
{
$color = imageColorsForIndex($image_id,$i);
$R=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$G=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$B=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
imageColorSet($image_id, $a, $R, $G, $B);
}

using an image (in this case I'm using a JPEG) that is a true color
image I was unable to successfully use imagecopymergegray since that
washed out my hues/saturation altogether making the image illegible
(imagecopymergegray + imagecreate); otherwise, the colors overrode
imagecopymergegray (imagecopymergegray + imagecreatetruecolor).

Using the code I borrowed I was able to change the image.. except that
it turned jet black instead!

Has anyone ever successfully grayscaled an image using GD library? If
so, how did you do it?

Thanx
Phil

[Phil Powell]

I'm sorry but that too breaks. Perhaps a code review is in order, I
realize that imageColorsTotal($this->image) produces 0, which I am
afraid I don't understand:

class ImageGrayscaleGenerator {

/*---------------------------------------------------------------------------------------------------------------------------------------------------------
This class exists due to the rather poor performance of the
imagecopymergegray() 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.
-----------------------------------------------------------------------------------------------------------------------------------------------------------*/

var $image, $image_width, $image_height;

// REMEMBER TO USE REFERENCE POINTER ONTO $image OBJECT TO ENSURE
"static" CHANGE TO OBJECT AND NOT TO INSTANCE

function ImageGrayscaleGenerator(&$image) { // CONSTRUCTOR
$this->image =& $image;
}

function makeGray() { // VOID METHOD
print_r($this->image); print_r("<P>");
print_r(@imageColorsTotal($this->image) . "<P>");
for ($i = 0; $i < @imagecolorstotal($this->image); $i++) {
$colorArray = @imageColorsForIndex($this->image, $i);
print_r($colorArray); print_r("<P>");
$avg = floor(($colorArray['red'] + $colorArray['green'] +
$colorArray['blue']) / 3);
@imageColorSet($this->image, $i, $avg, $avg, $avg);
}
}
}
Thanx
Phil

"CountScubula" <[e-mail]> wrote in message news:<_r*******************@newssvr27.news.prodigy .com>...

Try running an average of the three colors:
$avg = floor( ( $color['red']) + $color['green']) + $color['blue']) ) / 3 )
$R= $avg; $B = $avg; $G = $avg;
imageColorSet($image_id, $a, $R, $G, $B);
--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c*************************@posting.google.co m...

I borrowed this code from a source:

for($a=0;$a<imagecolorstotal ($image_id);$a++)
{
$color = imageColorsForIndex($image_id,$i);
$R=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$G=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$B=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
imageColorSet($image_id, $a, $R, $G, $B);
}

using an image (in this case I'm using a JPEG) that is a true color
image I was unable to successfully use imagecopymergegray since that
washed out my hues/saturation altogether making the image illegible
(imagecopymergegray + imagecreate); otherwise, the colors overrode
imagecopymergegray (imagecopymergegray + imagecreatetruecolor).

Using the code I borrowed I was able to change the image.. except that
it turned jet black instead!

Has anyone ever successfully grayscaled an image using GD library? If
so, how did you do it?

Thanx
Phil

[CountScubula]

sorry, I didnt really look at the code, how is it breaking, error, not
working?

--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

I'm sorry but that too breaks. Perhaps a code review is in order, I
realize that imageColorsTotal($this->image) produces 0, which I am
afraid I don't understand:

class ImageGrayscaleGenerator {

/*--------------------------------------------------------------------------
----------------------------------------------------------------------------
--- This class exists due to the rather poor performance of the
imagecopymergegray() 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.
-------------------------------------------------------------------------- ----------------------------------------------------------------------------
-----*/
var $image, $image_width, $image_height;

// REMEMBER TO USE REFERENCE POINTER ONTO $image OBJECT TO ENSURE
"static" CHANGE TO OBJECT AND NOT TO INSTANCE

function ImageGrayscaleGenerator(&$image) { // CONSTRUCTOR
$this->image =& $image;
}

function makeGray() { // VOID METHOD
print_r($this->image); print_r("<P>");
print_r(@imageColorsTotal($this->image) . "<P>");
for ($i = 0; $i < @imagecolorstotal($this->image); $i++) {
$colorArray = @imageColorsForIndex($this->image, $i);
print_r($colorArray); print_r("<P>");
$avg = floor(($colorArray['red'] + $colorArray['green'] +
$colorArray['blue']) / 3);
@imageColorSet($this->image, $i, $avg, $avg, $avg);
}
}
}
Thanx
Phil

"CountScubula" <[e-mail]> wrote in message

news:<_r*******************@newssvr27.news.prodigy .com>...

Try running an average of the three colors:
$avg = floor( ( $color['red']) + $color['green']) + $color['blue']) ) / 3 ) $R= $avg; $B = $avg; $G = $avg;
imageColorSet($image_id, $a, $R, $G, $B);
--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c*************************@posting.google.co m...

I borrowed this code from a source:

for($a=0;$a<imagecolorstotal ($image_id);$a++)
{
$color = imageColorsForIndex($image_id,$i);
$R=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$G=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
$B=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
($color['blue']);
imageColorSet($image_id, $a, $R, $G, $B);
}

using an image (in this case I'm using a JPEG) that is a true color
image I was unable to successfully use imagecopymergegray since that
washed out my hues/saturation altogether making the image illegible
(imagecopymergegray + imagecreate); otherwise, the colors overrode
imagecopymergegray (imagecopymergegray + imagecreatetruecolor).

Using the code I borrowed I was able to change the image.. except that
it turned jet black instead!

Has anyone ever successfully grayscaled an image using GD library? If
so, how did you do it?

Thanx
Phil

[Phil Powell]

"CountScubula" <[e-mail]> wrote in message news:<bE******************@newssvr27.news.prodigy. com>...

sorry, I didnt really look at the code, how is it breaking, error, not
working?

I'll show you, just go down and view...

Phil

--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

I'm sorry but that too breaks. Perhaps a code review is in order, I
realize that imageColorsTotal($this->image) produces 0, which I am
afraid I don't understand:

class ImageGrayscaleGenerator {

/*--------------------------------------------------------------------------
----------------------------------------------------------------------------
---

This class exists due to the rather poor performance of the
imagecopymergegray() 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.
--------------------------------------------------------------------------

----------------------------------------------------------------------------
-----*/

var $image, $image_width, $image_height;

// REMEMBER TO USE REFERENCE POINTER ONTO $image OBJECT TO ENSURE
"static" CHANGE TO OBJECT AND NOT TO INSTANCE

function ImageGrayscaleGenerator(&$image) { // CONSTRUCTOR
$this->image =& $image;
}

function makeGray() { // VOID METHOD
print_r($this->image); print_r("<P>");
print_r(@imageColorsTotal($this->image) . "<P>");
** STOP HERE! What happens is that imageColorsTotal($this->image) =
0! Though the image is in color and I do a reference pointer to the
$image resource paramters in the method call, and it actually DOES
change the image according to the value of
imageColorsTotal($this->image), it turns the entire image into one
jet-black image, no tone, no hue, nothing, a big black box.

Phil

for ($i = 0; $i < @imagecolorstotal($this->image); $i++) {
$colorArray = @imageColorsForIndex($this->image, $i);
print_r($colorArray); print_r("<P>");
$avg = floor(($colorArray['red'] + $colorArray['green'] +
$colorArray['blue']) / 3);
@imageColorSet($this->image, $i, $avg, $avg, $avg);
}
}
}
Thanx
Phil

"CountScubula" <[e-mail]> wrote in message

news:<_r*******************@newssvr27.news.prodigy .com>... Try running an average of the three colors:
$avg = floor( ( $color['red']) + $color['green']) + $color['blue']) ) / 3 ) $R= $avg; $B = $avg; $G = $avg;
imageColorSet($image_id, $a, $R, $G, $B);
--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c*************************@posting.google.co m...
> I borrowed this code from a source:
>
>
>
> for($a=0;$a<imagecolorstotal ($image_id);$a++)
> {
> $color = imageColorsForIndex($image_id,$i);
> $R=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
> ($color['blue']);
> $G=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
> ($color['blue']);
> $B=.299 * ($color['red'])+ .587 * ($color['green'])+ .114 *
> ($color['blue']);
> imageColorSet($image_id, $a, $R, $G, $B);
> }
>
> using an image (in this case I'm using a JPEG) that is a true color
> image I was unable to successfully use imagecopymergegray since that
> washed out my hues/saturation altogether making the image illegible
> (imagecopymergegray + imagecreate); otherwise, the colors overrode
> imagecopymergegray (imagecopymergegray + imagecreatetruecolor).
>
> Using the code I borrowed I was able to change the image.. except that
> it turned jet black instead!
>
> Has anyone ever successfully grayscaled an image using GD library? If
> so, how did you do it?
>
> Thanx
> Phil

[CountScubula]

"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

I'll show you, just go down and view...

Phil

< Big-O-snip >

Sometimes easier to re-invent the wheel (thats my my cars don't have model-t
wheels on them)
here is some code that works, and you can test here:
http://www.gzentools.com/test/img2gry.php

<?php

$imgFile = "girl1.jpg";

$imSrc = imagecreatefromjpeg($imgFile);

$imW = imagesx($imSrc);
$imH = imagesy($imSrc);

$imDst = imagecreate($imW,$imH);

// create 256 shades of grey
for ($i=0; $i<256; $i++) {
$colorNdx[$i] = imagecolorallocate($imDst,$i,$i,$i);
}

for ($y=0; $y<$imH; $y++)
{
for ($x=0; $x<$imW; $x++)
{
$ndx = imagecolorat($imSrc,$x,$y);
$ndxColors = imagecolorsforindex($imSrc,$ndx);
$avg = floor( ($ndxColors['red'] + $ndxColors['green'] +
$ndxColors['blue']) / 3 );
imagesetpixel($imDst,$x,$y,$colorNdx[$avg]);
}
}

imagejpeg($imDst);
exit();

?>
--
Mike Bradley
http://www.gzentools.com -- free online php tools

[Phil Powell]

IT WORKED AT LAST!!! Thanx a lot. By the way, your URL produced
ASCII-related garbage on my screen, just so you know.

Thanx again!!
Phil

"CountScubula" <[e-mail]> wrote in message news:<vi*******************@newssvr27.news.prodigy .com>...

"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

I'll show you, just go down and view...

Phil

< Big-O-snip >

Sometimes easier to re-invent the wheel (thats my my cars don't have model-t
wheels on them)
here is some code that works, and you can test here:
http://www.gzentools.com/test/img2gry.php

<?php

$imgFile = "girl1.jpg";

$imSrc = imagecreatefromjpeg($imgFile);

$imW = imagesx($imSrc);
$imH = imagesy($imSrc);

$imDst = imagecreate($imW,$imH);

// create 256 shades of grey
for ($i=0; $i<256; $i++) {
$colorNdx[$i] = imagecolorallocate($imDst,$i,$i,$i);
}

for ($y=0; $y<$imH; $y++)
{
for ($x=0; $x<$imW; $x++)
{
$ndx = imagecolorat($imSrc,$x,$y);
$ndxColors = imagecolorsforindex($imSrc,$ndx);
$avg = floor( ($ndxColors['red'] + $ndxColors['green'] +
$ndxColors['blue']) / 3 );
imagesetpixel($imDst,$x,$y,$colorNdx[$avg]);
}
}

imagejpeg($imDst);
exit();

?>

[CountScubula]

Like like I forgot to inflate the tire after I reinvented the wheel, forgot
to put:
header("Content-type: image/jpeg");

--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

IT WORKED AT LAST!!! Thanx a lot. By the way, your URL produced
ASCII-related garbage on my screen, just so you know.

Thanx again!!
Phil

"CountScubula" <[e-mail]> wrote in message

news:<vi*******************@newssvr27.news.prodigy .com>...

"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

I'll show you, just go down and view...

Phil

< Big-O-snip >

Sometimes easier to re-invent the wheel (thats my my cars don't have model-t wheels on them)
here is some code that works, and you can test here:
http://www.gzentools.com/test/img2gry.php

<?php

$imgFile = "girl1.jpg";

$imSrc = imagecreatefromjpeg($imgFile);

$imW = imagesx($imSrc);
$imH = imagesy($imSrc);

$imDst = imagecreate($imW,$imH);

// create 256 shades of grey
for ($i=0; $i<256; $i++) {
$colorNdx[$i] = imagecolorallocate($imDst,$i,$i,$i);
}

for ($y=0; $y<$imH; $y++)
{
for ($x=0; $x<$imW; $x++)
{
$ndx = imagecolorat($imSrc,$x,$y);
$ndxColors = imagecolorsforindex($imSrc,$ndx);
$avg = floor( ($ndxColors['red'] + $ndxColors['green'] +
$ndxColors['blue']) / 3 );
imagesetpixel($imDst,$x,$y,$colorNdx[$avg]);
}
}

imagejpeg($imDst);
exit();

?>

[Phil Powell]

Sorry I can't add that header() line, the moment I do, "index.php"
turns literally into an indiscernible JPEG image (that's assuming I'm
working with a JPEG, in my Image Catalog it could literally be
anything, even a video!)

Phil

"CountScubula" <[e-mail]> wrote in message news:<VP*****************@newssvr29.news.prodigy.c om>...

Like like I forgot to inflate the tire after I reinvented the wheel, forgot
to put:
header("Content-type: image/jpeg");

--
Mike Bradley
http://www.gzentools.com -- free online php tools
"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...

IT WORKED AT LAST!!! Thanx a lot. By the way, your URL produced
ASCII-related garbage on my screen, just so you know.

Thanx again!!
Phil

"CountScubula" <[e-mail]> wrote in message

news:<vi*******************@newssvr27.news.prodigy .com>...

"Phil Powell" <so*****@erols.com> wrote in message
news:1c**************************@posting.google.c om...
>
> I'll show you, just go down and view...
>
> Phil
>
> < Big-O-snip >

Sometimes easier to re-invent the wheel (thats my my cars don't have model-t wheels on them)
here is some code that works, and you can test here:
http://www.gzentools.com/test/img2gry.php

<?php

$imgFile = "girl1.jpg";

$imSrc = imagecreatefromjpeg($imgFile);

$imW = imagesx($imSrc);
$imH = imagesy($imSrc);

$imDst = imagecreate($imW,$imH);

// create 256 shades of grey
for ($i=0; $i<256; $i++) {
$colorNdx[$i] = imagecolorallocate($imDst,$i,$i,$i);
}

for ($y=0; $y<$imH; $y++)
{
for ($x=0; $x<$imW; $x++)
{
$ndx = imagecolorat($imSrc,$x,$y);
$ndxColors = imagecolorsforindex($imSrc,$ndx);
$avg = floor( ($ndxColors['red'] + $ndxColors['green'] +
$ndxColors['blue']) / 3 );
imagesetpixel($imDst,$x,$y,$colorNdx[$avg]);
}
}

imagejpeg($imDst);
exit();

?>