How Can PHP Compare Two Images for Similarity

Image comparison class: image.compare.class.php

mimeType()

First of all we will use our mimeType function. This function will tell us the MIME type of the image. If it is JPEG or PNG than it will return the MIME type. Otherwise it will return false.

This function will take an image file name as parameter for checking the extension of the image file name.

resizeImage()

After knowing the MIME type we will resize our image in blocks of 8 x 8 pixels.

resizeImage() takes two parameters. This function takes the MIME type from the source image and calls the createImage function using the image source. The resizeimage function will save the resized image.

createImage()

The createImage function will check whether the MIME type is of JPEG or PNG. If the condition satisfied than we will call the imagecreatefromjpeg() or imagecreatefrompng(). Otherwise it will just return the false. This function is also used by the resizeImage for creating the resized image.

colorMeanValue()

We will use the colorMeanValue function to take out the color mean value of the image. It will also list the pixels of the colors. This function will return the mean value array.

bits()

Now we will our bits function which will take the colorMeanValue array as parameter. This value will take out the bit value in 0,1. If a color value is higher than the mean value, it will be 1 otherwise it will be 0.

compare()

After calling all the functions we will use our image comparison or image similarity function to find out the difference. This compare function will take 2 images to compare them, so we have 2 images with us, one is our original image and another one is our resized image.

This function will call the createImage() for both the images and check the return value. When it returns true we will resize both the images and use the image filter for both the images.

Then we will take out the colorMeanValue of both the images and pass the values to the bits function to get the bit value of the images. After getting the bit values we will use the for function and calculate the values of both the images.

If the calculated value difference is less than or equal to 10 than you can say that image is similar, otherwise there is some difference in the image.

This is the main function which will compare image similarity by using all the above functions and provide the image comparison value.

For using the image comparison class we will use our index file and call our image compare function.

The processing script: demo.php

$class = new compareImages;
echo $class->compare('1.jpg','2.jpg');

In the demo.php script we will include our image comparison class and call the compare function to take out the 2 images similarity level value.

Download and Install the PHP Compare Images Similarity