Drawing graphic lines using PHP GD Support

imageline($image,$x1,$y1,$x2,$y2,$color)
$imageImage created using ImageCreate() or imagecreatetruecolor()
$x1X coordinate of start point ( X : Horizontal )
$y1Y coordinate of start point ( Y : Vertical)
$x2X coordinate of end point ( X : Horizontal )
$y2Y coordinate of end point ( Y : Vertical )
$colorColor of the line by using imagecolorallocate().
If you have installed GD library then let us try to draw some lines in an image using gd support. We will open our file in a new window as we have to tell browser ( through header ) that we are sending image.

Using gd we will first learn how to draw line. We will learn some basic functions used in creating and managing images.
$im = @ImageCreate (100, 200)
The above line creates and image identifier of width 100 and height 200. The top left coordinate is set as 0, 0

Drawing lines and patterns using different thickness and colours using imageline() in PHP GD
$background_color = ImageColorAllocate ($im, 234, 234, 234);
Background color is set here for the image with the identifier $im. Here we have set it to a light gray background. The color of the background can be changed by changing the values of red, green, blue ( now all are set to 234 to create light gray background)

Same way let us set a text color for the image
$text_color = ImageColorAllocate ($im, 233, 14, 91);
imageline ($im,$x1,$y1,$x2,$y2,$text_color);
The above line will show the line from where to where it is to be drawn. Staring from $x1,$x2 to $x2, $y2. Note that top left is at the coordinate 0,0. The lines below will give how the line will appear with different values of the coordinates used in imageline function.

Now with this image, let us draw
ImagePng ($im);
With the above knowledge, you can see that the command imageline ($im,$x1,$y1,$x2,$y2,$text_color) draws lines between two points defined with two coordinates. To learn the different images we get ( or different lines ) with the change in value of coordinates ( x and y ) we will list a set of values and corresponding image link. Click the link right of the coordinates to check what image will be drawn with the value given at left. All images will be opened in a new window.

imageline ($im,0,0,50,100,$text_color)Display
imageline ($im,0,0,100,100,$text_color) Display
imageline ($im,100,0,0,200,$text_color) Display
imageline ($im,0,0,100,200,$text_color) Display

With above example you can see how the coordinates affect the line inside the image. Now let us dray two lines in the same image one after the other.

imageline ($im,0,0,100,200,$text_color);
imageline ($im,100,0,0,200,$text_color);
Display


Above examples must have given you some idea on how to draw lines using gd support in PHP. You can use the forum if you have any doubt. Now here you can see the code we used to draw the lines in small window. Note that this code has two imageline functions to draw two lines. Change the data and see how the line changes.

<?php
header ("Content-type: image/png"); $x1=$_GET['x1']; $x2=$_GET['x2']; $y1=$_GET['y1']; $y2=$_GET['y2']; $im = @ImageCreate (100, 200) or die ("Cannot Initialize new GD image stream"); $background_color = ImageColorAllocate ($im, 224, 234, 234); $text_color = ImageColorAllocate ($im, 233, 14, 91);
// imageline ($im,$x1,$y1,$x2,$y2,$text_color); imageline ($im,0,0,100,200,$text_color); imageline ($im,100,0,0,200,$text_color); ImagePng ($im); ?>
Save the above code in a file and open it without adding any html code or data to it. With this learning on how to draw lines we will move to our next learning.

Example

Note that PHP counts from 0, so if we take width as 600 then for the last line when $i=600 can't be drawn at the edge of the image so we kept width and height as 601 and 401. You can experiment this by changing width height to 600 and 400.
sample gd image with line
<?Php
header ("Content-type: image/jpeg");
$im = @ImageCreate (601, 401) // added one pixel for border
or die ("Cannot Initialize new GD image stream");
$gap=20; // change this value to increase the lines 
$background_color = ImageColorAllocate ($im, 255, 255, 255);
$text_color = ImageColorAllocate ($im, 128, 255, 136);
//imagesetthickness($im, 5);
for($i=0;$i<=600;$i +=$gap){
imageline ($im,$i,0,$i,400,$text_color);
}
for($i=0;$i<=400;$i +=$gap){
imageline ($im,0,$i,600,$i,$text_color);
}
Imagejpeg ($im);
imagedestroy($im); //memory is removed. 
?>
We can use different color for horizontal lines
sample gd image with color line
header ("Content-type: image/jpeg");
$im = @ImageCreate (601, 401) // added one pixel for border
or die ("Cannot Initialize new GD image stream");
$size=20; // change this value to increase the lines 
$background_color = ImageColorAllocate ($im, 255, 255, 255);
$text_color = ImageColorAllocate ($im, 128, 255, 136);
//imagesetthickness($im, 5);
// vertical lines 
for($i=0;$i<=600;$i +=$size){
imageline ($im,$i,0,$i,400,$text_color);
}
// Horizontal lines 
$text_color = ImageColorAllocate ($im, 255, 128, 128);
for($i=0;$i<=400;$i +=$size){
imageline ($im,0,$i,600,$i,$text_color);
}
Imagejpeg ($im);
imagedestroy($im); //memory is removed. 
By using random number generator rand(min,max) we can create all lines in different colours.
sample gd image with random color line
header ("Content-type: image/jpeg");
$im = @ImageCreate (601, 401) // added one pixel for border
or die ("Cannot Initialize new GD image stream");
$size=20; // change this value to increase the lines 
$background_color = ImageColorAllocate ($im, 255, 255, 255);

for($i=0;$i<=600;$i +=$size){
$r=rand(1,255);
$g=rand(1,255);
$b=rand(1,255);	
$text_color = ImageColorAllocate ($im, $r, $g,$b);	
imageline ($im,$i,0,$i,400,$text_color);
}
// Horizontal lines 

for($i=0;$i<=400;$i +=$size){
$r=rand(1,255);
$g=rand(1,255);
$b=rand(1,255);	
$text_color = ImageColorAllocate ($im, $r, $g,$b);	
imageline ($im,0,$i,600,$i,$text_color);
}
Imagejpeg ($im);
imagedestroy($im); //memory is removed. 

Managing thickness of lines

sample gd image with different thinkness color line
Add this line before the for loop in above code.
imagesetthickness($im, 5);

.
Draw SIN & COS curve using imageline()
GD functions GD imagearc() GD imagerectangle()

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