path: root/user_guide_src/source/libraries/image_lib.rst

########################
Image Manipulation Class
########################

CodeIgniter's Image Manipulation class lets you perform the following
actions:

-  Image Resizing
-  Thumbnail Creation
-  Image Cropping
-  Image Rotating
-  Image Watermarking

All three major image libraries are supported: GD/GD2, NetPBM, and
ImageMagick

.. note:: Watermarking is only available using the GD/GD2 library. In
	addition, even though other libraries are supported, GD is required in
	order for the script to calculate the image properties. The image
	processing, however, will be performed with the library you specify.

**********************
Initializing the Class
**********************

Like most other classes in CodeIgniter, the image class is initialized
in your controller using the $this->load->library function::

	$this->load->library('image_lib');

Once the library is loaded it will be ready for use. The image library
object you will use to call all functions is: $this->image_lib

Processing an Image
===================

Regardless of the type of processing you would like to perform
(resizing, cropping, rotation, or watermarking), the general process is
identical. You will set some preferences corresponding to the action you
intend to perform, then call one of four available processing functions.
For example, to create an image thumbnail you'll do this::

	$config['image_library'] = 'gd2';
	$config['source_image']	= '/path/to/image/mypic.jpg';
	$config['create_thumb'] = TRUE;
	$config['maintain_ratio'] = TRUE;
	$config['width']	 = 75;
	$config['height']	= 50;

	$this->load->library('image_lib', $config); 

	$this->image_lib->resize();

The above code tells the image_resize function to look for an image
called *mypic.jpg* located in the source_image folder, then create a
thumbnail that is 75 X 50 pixels using the GD2 image_library. Since the
maintain_ratio option is enabled, the thumb will be as close to the
target width and height as possible while preserving the original aspect
ratio. The thumbnail will be called *mypic_thumb.jpg*

.. note:: In order for the image class to be allowed to do any
	processing, the folder containing the image files must have write
	permissions.

.. note:: Image processing can require a considerable amount of server
	memory for some operations. If you are experiencing out of memory errors
	while processing images you may need to limit their maximum size, and/or
	adjust PHP memory limits.

Processing Functions
====================

There are four available processing functions:

-  $this->image_lib->resize()
-  $this->image_lib->crop()
-  $this->image_lib->rotate()
-  $this->image_lib->watermark()
-  $this->image_lib->clear()

These functions return boolean TRUE upon success and FALSE for failure.
If they fail you can retrieve the error message using this function::

	echo $this->image_lib->display_errors();

A good practice is use the processing function conditionally, showing an
error upon failure, like this::

	if ( ! $this->image_lib->resize())
	{
	    echo $this->image_lib->display_errors();
	}

Note: You can optionally specify the HTML formatting to be applied to
the errors, by submitting the opening/closing tags in the function, like
this::

	$this->image_lib->display_errors('<p>', '</p>');

Preferences
===========

The preferences described below allow you to tailor the image processing
to suit your needs.

Note that not all preferences are available for every function. For
example, the x/y axis preferences are only available for image cropping.
Likewise, the width and height preferences have no effect on cropping.
The "availability" column indicates which functions support a given
preference.

Availability Legend:

-  R - Image Resizing
-  C - Image Cropping
-  X - Image Rotation
-  W - Image Watermarking

Preference
Default Value
Options
Description
Availability
**image_library**
GD2
GD, GD2, ImageMagick, NetPBM
Sets the image library to be used.
R, C, X, W
**library_path**
None
None
Sets the server path to your ImageMagick or NetPBM library. If you use
either of those libraries you must supply the path.
R, C, X
**source_image**
None
None
Sets the source image name/path. The path must be a relative or absolute
server path, not a URL.
R, C, S, W
**dynamic_output**
FALSE
TRUE/FALSE (boolean)
Determines whether the new image file should be written to disk or
generated dynamically. Note: If you choose the dynamic setting, only one
image can be shown at a time, and it can't be positioned on the page. It
simply outputs the raw image dynamically to your browser, along with
image headers.
R, C, X, W
**quality**
90%
1 - 100%
Sets the quality of the image. The higher the quality the larger the
file size.
R, C, X, W
**new_image**
None
None
Sets the destination image name/path. You'll use this preference when
creating an image copy. The path must be a relative or absolute server
path, not a URL.
R, C, X, W
**width**
None
None
Sets the width you would like the image set to.
R, C
**height**
None
None
Sets the height you would like the image set to.
R, C
**create_thumb**
FALSE
TRUE/FALSE (boolean)
Tells the image processing function to create a thumb.
R
**thumb_marker**
_thumb
None
Specifies the thumbnail indicator. It will be inserted just before the
file extension, so mypic.jpg would become mypic_thumb.jpg
R
**maintain_ratio**
TRUE
TRUE/FALSE (boolean)
Specifies whether to maintain the original aspect ratio when resizing or
use hard values.
R, C
**master_dim**
auto
auto, width, height
Specifies what to use as the master axis when resizing or creating
thumbs. For example, let's say you want to resize an image to 100 X 75
pixels. If the source image size does not allow perfect resizing to
those dimensions, this setting determines which axis should be used as
the hard value. "auto" sets the axis automatically based on whether the
image is taller then wider, or vice versa.
R
**rotation_angle**
None
90, 180, 270, vrt, hor
Specifies the angle of rotation when rotating images. Note that PHP
rotates counter-clockwise, so a 90 degree rotation to the right must be
specified as 270.
X
**x_axis**
None
None
Sets the X coordinate in pixels for image cropping. For example, a
setting of 30 will crop an image 30 pixels from the left.
C
**y_axis**
None
None
Sets the Y coordinate in pixels for image cropping. For example, a
setting of 30 will crop an image 30 pixels from the top.
C
Setting preferences in a config file
====================================

If you prefer not to set preferences using the above method, you can
instead put them into a config file. Simply create a new file called
image_lib.php, add the $config array in that file. Then save the file
in: config/image_lib.php and it will be used automatically. You will
NOT need to use the $this->image_lib->initialize function if you save
your preferences in a config file.

$this->image_lib->resize()
===========================

The image resizing function lets you resize the original image, create a
copy (with or without resizing), or create a thumbnail image.

For practical purposes there is no difference between creating a copy
and creating a thumbnail except a thumb will have the thumbnail marker
as part of the name (ie, mypic_thumb.jpg).

All preferences listed in the table above are available for this
function except these three: rotation_angle, x_axis, and y_axis.

Creating a Thumbnail
--------------------

The resizing function will create a thumbnail file (and preserve the
original) if you set this preference to TRUE::

	$config['create_thumb'] = TRUE;

This single preference determines whether a thumbnail is created or not.

Creating a Copy
---------------

The resizing function will create a copy of the image file (and preserve
the original) if you set a path and/or a new filename using this
preference::

	$config['new_image'] = '/path/to/new_image.jpg';

Notes regarding this preference:

-  If only the new image name is specified it will be placed in the same
   folder as the original
-  If only the path is specified, the new image will be placed in the
   destination with the same name as the original.
-  If both the path and image name are specified it will placed in its
   own destination and given the new name.

Resizing the Original Image
---------------------------

If neither of the two preferences listed above (create_thumb, and
new_image) are used, the resizing function will instead target the
original image for processing.

$this->image_lib->crop()
=========================

The cropping function works nearly identically to the resizing function
except it requires that you set preferences for the X and Y axis (in
pixels) specifying where to crop, like this::

	$config['x_axis'] = '100';
	$config['y_axis'] = '40';

All preferences listed in the table above are available for this
function except these: rotation_angle, width, height, create_thumb,
new_image.

Here's an example showing how you might crop an image::

	$config['image_library'] = 'imagemagick';
	$config['library_path'] = '/usr/X11R6/bin/';
	$config['source_image']	= '/path/to/image/mypic.jpg';
	$config['x_axis'] = '100';
	$config['y_axis'] = '60';

	$this->image_lib->initialize($config); 

	if ( ! $this->image_lib->crop())
	{
	    echo $this->image_lib->display_errors();
	}

Note: Without a visual interface it is difficult to crop images, so this
function is not very useful unless you intend to build such an
interface. That's exactly what we did using for the photo gallery module
in ExpressionEngine, the CMS we develop. We added a JavaScript UI that
lets the cropping area be selected.

$this->image_lib->rotate()
===========================

The image rotation function requires that the angle of rotation be set
via its preference::

	$config['rotation_angle'] = '90';

There are 5 rotation options:

#. 90 - rotates counter-clockwise by 90 degrees.
#. 180 - rotates counter-clockwise by 180 degrees.
#. 270 - rotates counter-clockwise by 270 degrees.
#. hor - flips the image horizontally.
#. vrt - flips the image vertically.

Here's an example showing how you might rotate an image::

	$config['image_library'] = 'netpbm';
	$config['library_path'] = '/usr/bin/';
	$config['source_image']	= '/path/to/image/mypic.jpg';
	$config['rotation_angle'] = 'hor';

	$this->image_lib->initialize($config); 

	if ( ! $this->image_lib->rotate())
	{
	    echo $this->image_lib->display_errors();
	}

$this->image_lib->clear()
==========================

The clear function resets all of the values used when processing an
image. You will want to call this if you are processing images in a
loop.

::

	$this->image_lib->clear();


******************
Image Watermarking
******************

The Watermarking feature requires the GD/GD2 library.

Two Types of Watermarking
=========================

There are two types of watermarking that you can use:

-  **Text**: The watermark message will be generating using text, either
   with a True Type font that you specify, or using the native text
   output that the GD library supports. If you use the True Type version
   your GD installation must be compiled with True Type support (most
   are, but not all).
-  **Overlay**: The watermark message will be generated by overlaying an
   image (usually a transparent PNG or GIF) containing your watermark
   over the source image.

Watermarking an Image
=====================

Just as with the other functions (resizing, cropping, and rotating) the
general process for watermarking involves setting the preferences
corresponding to the action you intend to perform, then calling the
watermark function. Here is an example::

	$config['source_image']	= '/path/to/image/mypic.jpg';
	$config['wm_text'] = 'Copyright 2006 - John Doe';
	$config['wm_type'] = 'text';
	$config['wm_font_path'] = './system/fonts/texb.ttf';
	$config['wm_font_size']	= '16';
	$config['wm_font_color'] = 'ffffff';
	$config['wm_vrt_alignment'] = 'bottom';
	$config['wm_hor_alignment'] = 'center';
	$config['wm_padding'] = '20';

	$this->image_lib->initialize($config); 

	$this->image_lib->watermark();

The above example will use a 16 pixel True Type font to create the text
"Copyright 2006 - John Doe". The watermark will be positioned at the
bottom/center of the image, 20 pixels from the bottom of the image.

.. note:: In order for the image class to be allowed to do any
	processing, the image file must have "write" file permissions. For
	example, 777.

Watermarking Preferences
========================

This table shown the preferences that are available for both types of
watermarking (text or overlay)

Preference
Default Value
Options
Description
**wm_type**
text
text, overlay
Sets the type of watermarking that should be used.
**source_image**
None
None
Sets the source image name/path. The path must be a relative or absolute
server path, not a URL.
**dynamic_output**
FALSE
TRUE/FALSE (boolean)
Determines whether the new image file should be written to disk or
generated dynamically. Note: If you choose the dynamic setting, only one
image can be shown at a time, and it can't be positioned on the page. It
simply outputs the raw image dynamically to your browser, along with
image headers.
**quality**
90%
1 - 100%
Sets the quality of the image. The higher the quality the larger the
file size.
**padding**
None
A number
The amount of padding, set in pixels, that will be applied to the
watermark to set it away from the edge of your images.
**wm_vrt_alignment**
bottom
top, middle, bottom
Sets the vertical alignment for the watermark image.
**wm_hor_alignment**
center
left, center, right
Sets the horizontal alignment for the watermark image.
**wm_hor_offset**
None
None
You may specify a horizontal offset (in pixels) to apply to the
watermark position. The offset normally moves the watermark to the
right, except if you have your alignment set to "right" then your offset
value will move the watermark toward the left of the image.
**wm_vrt_offset**
None
None
You may specify a vertical offset (in pixels) to apply to the watermark
position. The offset normally moves the watermark down, except if you
have your alignment set to "bottom" then your offset value will move the
watermark toward the top of the image.
Text Preferences
----------------

This table shown the preferences that are available for the text type of
watermarking.

Preference
Default Value
Options
Description
**wm_text**
None
None
The text you would like shown as the watermark. Typically this will be a
copyright notice.
**wm_font_path**
None
None
The server path to the True Type Font you would like to use. If you do
not use this option, the native GD font will be used.
**wm_font_size**
16
None
The size of the text. Note: If you are not using the True Type option
above, the number is set using a range of 1 - 5. Otherwise, you can use
any valid pixel size for the font you're using.
**wm_font_color**
ffffff
None
The font color, specified in hex. Note, you must use the full 6
character hex value (ie, 993300), rather than the three character
abbreviated version (ie fff).
**wm_shadow_color**
None
None
The color of the drop shadow, specified in hex. If you leave this blank
a drop shadow will not be used. Note, you must use the full 6 character
hex value (ie, 993300), rather than the three character abbreviated
version (ie fff).
**wm_shadow_distance**
3
None
The distance (in pixels) from the font that the drop shadow should
appear.
Overlay Preferences
-------------------

This table shown the preferences that are available for the overlay type
of watermarking.

Preference
Default Value
Options
Description
**wm_overlay_path**
None
None
The server path to the image you wish to use as your watermark. Required
only if you are using the overlay method.
**wm_opacity**
50
1 - 100
Image opacity. You may specify the opacity (i.e. transparency) of your
watermark image. This allows the watermark to be faint and not
completely obscure the details from the original image behind it. A 50%
opacity is typical.
**wm_x_transp**
4
A number
If your watermark image is a PNG or GIF image, you may specify a color
on the image to be "transparent". This setting (along with the next)
will allow you to specify that color. This works by specifying the "X"
and "Y" coordinate pixel (measured from the upper left) within the image
that corresponds to a pixel representative of the color you want to be
transparent.
**wm_y_transp**
4
A number
Along with the previous setting, this allows you to specify the
coordinate to a pixel representative of the color you want to be
transparent.