php gd functions are cool

I recently discovered that my host has the gd functions installed on the server.

This opens up so many possibilities.

You can see an example here:

6CULTURES

part of the php script:

Code:

$im = imagecreatefrompng("117bw.png");
$rgb = imagecolorat($im, 896, 850);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;

$c = $r.", ".$g.", ".$b;

echo "<P>rgb of 896, 850 = ".$c."</P>";

Why is this cool

Suppose I wanted a really big map and I want to have navies and armies on this map, but that some paths are blocked for these armies, and that navies obviously can't sail on land. I could do this manually, by making a huge database, but this would be an incredibly boring and tedious task, and it would take days if not weeks to complete this database.

Not so with GD functions!

Now all I have to do is draw a map with MS paint. Save it as a bitmap and use gimp to convert it to a png file. Then I can just fetch the rgb value of the pixel.

For example: If the rgb value corresponds to blue, it is water, if it corresponds to green, it is land.

Do I hear you say cool?!

 

I made a random version of this.

Shugo 6

 

I do notice the limits of these gd functions. They take a lot of time and computer resources to complete.

Looping through a 1000 by 1000 pixels or more, one at a time is too much effort for the server it seems.

I am currently looking for a way to count the number of pixels of a certain color in an image, but there doesn't appear to be such a GD function.

 

by the way, there is also a native alternative version of GD as an php image editing library.

Do you know what it is called?










Cairo

 

already have lots of books about php and this one doesn't appear to be downloadable, but thanks anyway

 

i am busy learning java myself


I already tried to make an applet, but it doesn't appear to be working yet. I probably made a mistake with an import of a class, or there is some sort of browser security blocking the applet.

Anyhow...
Sofar I find that 2d isometric view of a village seems to me to be the better option for the townview in shugo. I could try to make it 3d, but this feels complicated even for me. There is so much non-algebraic mathematics in 3d and this makes things difficult for me. I wasn't good at working with tan, cosinus and sinus in highschool and I'm still no good at it now. So that makes me decide I should try 2d isometric sprites.

I could try to make 2d isometric sprites with php and svg, but this would take a lot of layers. Even a small town of 4 by 4 grids, would take at least 7 layers. 5 by 5 requires 9 layers. Now imagine a 9 by 9 town, 17 layers is a lot.

 

I found a cumbersome way, to find out the number of pixels of a certain color in an image.

STEP 1

Open the bitmap in gimp

STEP 2

Save bitmap as an X PixMap (that's with a xpm extension)

STEP 3

Open the xpm with notepad

STEP 4

Replace the opening and closing of the rows with spaces (you basically remove them)

Remove the top rows

Replace the symbols that correspond to certain color values with letters in the alphabet

STEP 5

Save this as a txt file.

STEP 6

copy/paste all into the string that is the variable rgbstring

Code:

<?php

$rgbstring = "";

$afunc = substr_count($rgbstring, "a");

echo "<P>a ".$afunc."</P>";

?>

STEP 7

Save the php file.

STEP 8

Open the php file to see how many there are.

FINAL STEP

Copy/repeat and alter the last two lines of the code for the other letters (i.e. other colors).

EXPLANATION

With that piece of code I count how many letter "a" there are. I know that "a" is a shade of green, so now I know how many pixels there are of that shade of green.

IN CONCLUSION

I've been able to figure out this way, that about 82% is blue = sea in my map. About 7% is darkgreen = forest, about 4% is gray = mountains, and about 6% is lightgreen = ricefield. The remaining 1% are other colors.

 

The xpm map saves the color values in hex.

I found a hex to rgb convertor here:

Hex-to-RGB Color Converter

This makes it easier to figure out which letter is what color.

 

shouldn't really be a problem with php unless it's really big or you need lots of dynamic real time movement

 

you mean the map mentioned in this thread?

well I select a coordinate from the file, fetch the rgb value of the pixel and that's is how I know the color. Now suppose I fetch 25 of these pixels (5 x 5) next to eachother, that way I can make a grid appropriate to the map. The benefit of this is that I don't have to make the grid from fetching values from an sql database, because if the map is really big, that would mean, I need to make a really big database, which takes days to make.

 

Example

I made a nice little example, of the gd function.


A working example can de found here:

CAPOREGIME

Here is the code:

Code:

echo "<P><A HREF='cityfetch.php'>click here to refresh</A></P>";

$xrand = rand(1,663);
$yrand = rand(1,1380);
  
$im = imagecreatefrompng("city.png");

echo "<P>top left corner is ".$xrand.",".$yrand."</P>";

echo "<table>";


$x = 0;

while ($x <=6){

echo "<tr>";

$y = 0;

while ($y <=6){
$xr = $xrand + $x;
$yr = $yrand + $y;

$rgb = imagecolorat($im, $xr, $yr);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
$colo = $r.",".$g.",".$b;

echo "<td>  ".$colo."  </td>";

$y++;
}

$x++;

echo "</tr>";

}

echo "</table>";

echo "<IMG src='city.png' width='90%'>";