Posts Tagged with jpeg

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Resolved: JPG vs. JPEG image formats
posted by admin on June 18, 2016
I often use JPEG images, and I have noticed that there are two very similar file extensions: .jpg, which my mobile's camera and the Preview application use, and .jpeg, with which Image Capture saves the images from scanning with my Canon MX455 printer. LaTeX doesn't seem to distinguish, as I gave it a .jpeg with the extension changed to .jpg and the result seems to be the same as if it had been a .jpg right from the start. I have wondered what the difference between the two is. I have come across this question, and will certainly read through it, though at the moment I'm slightly out of time. However, from what I saw giving it a quick look, it seems not to distinguish the two extensions. In fact, it seems the file type's name is JPEG and the file extension is .jpg:

JPEG (or JPG, for the file extension; Joint Photographic Experts Group)

(excerpted from the first answer there). So is there any big difference between the two extensions? And if so, what is it?Read more
Wiki: PHP Dominant Colour Function with GD Librarywiki
posted by admin on April 13, 2016
Someone asked if it was possible to find the dominant colour (the more frequent colour, in %) of an image.

So I read about the GD PHP Library, which enables image support. I found the interesting function imageColorAt() which the colour of a specific pixel. Hence, my function consists of resizing to a known size, 100 x 100, then looping into each pixel, storing it’s colour into an array, then sorting the array to find the more frequent key.

Here’s the result :

function getDominantColour($image, $type='jpeg') // $type can be gif, jpeg or png
// This function needs GD Library enabled

eval('$source = imagecreatefrom' . $type . '("' . $image . '");'); // we load the source image
$source_x = imagesx($source); // source's X
$source_y = imagesy($source); // source's Y
$resized_x = 100; // resized image's X
$resized_y = 100; // resized image's Y
$resized= imagecreatetruecolor($resized_x, $resized_y); // we create a blank 100 x 100 image
imagecopyresampled($resized, $source, 0, 0, 0, 0, $resized_x, $resized_y, $source_x, $source_y); // We then copy and resized the source image into the blank image

// Required vars declaration
$colours = array();
$rgb = '';
$index = array();
for ($x=0; $x<100; $x++) // We loop into the pixels X
for ($y=0; $y<100; $y++) // We loop into the pixels Y
$rgb = imagecolorat($resized, $x, $y); // get the RGB of the pixel
$index = imagecolorsforindex($resized, $rgb); // Get the RGB Index
$key = 'R' . $index['red'] . 'G' . $index['green'] . 'B' . $index['blue']; // Put it into a string
if (empty($colours[$key])) // If it's the first time this colour is encountered
$colours[$key] = 1; // We give it a value of 1
} else { // If it's not the first time it is encountered
$colours[$key]++; // We increment its value
arsort($colours, SORT_NUMERIC); // We then sort the colours array so that the first one is the most frequent one
return key($colours); // we return the most frequent value

Working with images sure is fun. Looking forward to have more functions with the GD libraryRead more