PHP | ImagickPixelIterator getPreviousIteratorRow() Function

The ImagickPixelIterator::getPreviousIteratorRow() function is an inbuilt function in PHP which is used to get the previous row as an array of pixel wands from the pixel iterator.

Syntax:

array ImagickPixelIterator::getPreviousIteratorRow( void )

Parameters: This function doesn’t accepts any parameters.

Return Value: This function returns an array value containing ImagickPixel objects.

Below programs illustrate the ImagickPixelIterator::getPreviousIteratorRow() function in PHP:

Program 1:

<?php

// Create a new imagick object
$imagick = new Imagick(
'https://media.geeksforgeeks.org/wp-content/uploads/geeksforgeeks-13.png');

// Get the pixel iterator
$pixelIterator = $imagick->getPixelIterator();

// Set the pixel iterator to 50
$pixelIterator->setIteratorRow(50);

// Move one step to previous row
$pixelIterator->getPreviousIteratorRow();

// Get the current iterator row
echo "Current row is " . $pixelIterator->getIteratorRow();
?>

Output:

Current row is 49

Program 2:

<?php

// Create a new imagick object
$imagick = new Imagick();

// Create a image on imagick object
$imagick->newImage(800, 250, 'black');

$imageIterator = $imagick->getPixelIterator();

$x = 0;

// Set the iterator row to last row
$imageIterator->setIteratorRow(249);

while ($x < 250) {

    // Get the previous row
    $pixels = $imageIterator->getPreviousIteratorRow();

    foreach ($pixels as $pixel) {
        if ($x % 4) {

            // Set the color of pixel
            $pixel->setColor('green');

        } else {

            // Set the color of pixel
            $pixel->setColor('red');
        }
    }

    // Sync the iterator
    $imageIterator->syncIterator();

    $x++;
}

// Show the output
$imagick->setImageFormat('png');
header("Content-Type: image/png");
echo $imagick->getImageBlob();
?>

Output:

Reference: https://www.php.net/manual/en/imagickpixeliterator.getpreviousiteratorrow.php