Steps to use PHP and GD library to achieve image mosaic effect

Steps to achieve image mosaic effect using PHP and GD library

Introduction:
The mosaic effect is a method of dividing a picture into color blocks to form a decorative or privacy-protecting effect. Using PHP and GD libraries, we can easily achieve image mosaic effects. This article will introduce the steps to achieve the mosaic effect and provide corresponding code examples.

Step 1: Import pictures
First, we need to import a picture that needs to be processed. Upload the image to the server and get its path.

$sourceImagePath = 'path/to/source/image.jpg';
$sourceImage = imagecreatefromjpeg($sourceImagePath);

Step 2: Determine the size of the mosaic block
Next, we need to determine the size of the mosaic block. The size of the mosaic blocks determines the granularity of the final mosaic effect. We can adjust this value ourselves as needed.

$blockSize = 10;

Step 3: Create output image
According to the size of the image that requires the mosaic effect, we create a new image resource for output. The width and height of the output image can be calculated based on the width and height of the source image.

$sourceImageWidth = imagesx($sourceImage);
$sourceImageHeight = imagesy($sourceImage);

$outputImage = imagecreatetruecolor($sourceImageWidth, $sourceImageHeight);

Step 4: Process the image
Before processing the image, we need to traverse each mosaic block of the source image. Then, determine the average color inside each mosaic block and set all pixels in the mosaic block to that color.

for ($x = 0; $x < $sourceImageWidth; $x += $blockSize) {
    for ($y = 0; $y < $sourceImageHeight; $y += $blockSize) {
        $averageColor = getAverageColor($sourceImage, $x, $y, $blockSize);
        fillBlockWithColor($outputImage, $x, $y, $blockSize, $averageColor);
    }
}

// 获取马赛克块内的平均颜色
function getAverageColor($image, $startX, $startY, $blockSize) {
    $totalR = 0;
    $totalG = 0;
    $totalB = 0;
    $count = 0;

    for ($i = $startX; $i < $startX + $blockSize; $i++) {
        for ($j = $startY; $j < $startY + $blockSize; $j++) {
            $rgb = imagecolorat($image, $i, $j);
            $r = ($rgb >> 16) & 0xFF;
            $g = ($rgb >> 8) & 0xFF;
            $b = $rgb & 0xFF;

            $totalR += $r;
            $totalG += $g;
            $totalB += $b;
            $count++;
        }
    }

    $averageR = round($totalR / $count);
    $averageG = round($totalG / $count);
    $averageB = round($totalB / $count);

    return imagecolorallocate($image, $averageR, $averageG, $averageB);
}

// 将马赛克块填充为指定颜色
function fillBlockWithColor($image, $startX, $startY, $blockSize, $color) {
    imagefilledrectangle($image, $startX, $startY, $startX + $blockSize, $startY + $blockSize, $color);
}

Step 5: Output the image
Finally, we need to save the processed image to the server or output it directly to the browser.

$outputImagePath = 'path/to/output/image.jpg';
imagejpeg($outputImage, $outputImagePath);
imagedestroy($outputImage);

Conclusion:
Through the above steps, we can use PHP and GD libraries to achieve image mosaic effects. By adjusting the size of the mosaic blocks, we can control the granularity of the mosaic effect. I hope this article can help you understand and practice the process of creating mosaic effects.

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