Different effects of using imageflip() before and after adding image watermarks

M66 2025-05-17

In PHP, the imageflip() function is often used to flip an image. It can flip the image horizontally or vertically, or rotate 180 degrees. This operation is very useful when processing images, especially when we need to make various effects adjustments to the images. However, after watermarking the image, the effect of imageflip() may undergo some interesting changes. In this article, we will explore the differences in the imageflip() flip effect before and after adding a watermark.

1. Basic operation: Use of imageflip() function

The imageflip() function is part of the GD library in PHP and is often used to flip images. The basic syntax is as follows:

 imageflip($image, $mode);

Among them, $image is the resource of the target image, and $mode is the type of flip, which can be the following values:

IMG_FLIP_HORIZONTAL : Horizontal flip
IMG_FLIP_VERTICAL : vertical flip
IMG_FLIP_BOTH : Flip horizontally and vertically simultaneously

For example, the code for horizontally flipping an image is as follows:

 $image = imagecreatefromjpeg("image.jpg");
imageflip($image, IMG_FLIP_HORIZONTAL);
imagejpeg($image, "flipped_image.jpg");
imagedestroy($image);

This code flips the image horizontally and saves it as a new file flipped_image.jpg .

2. The effect of adding watermarks on image flip

We may need to add a watermark to the image before flipping it. The function of watermarks is usually to protect image copyrights or to enhance brand promotion. We achieve the effect of watermarking by adding text or images to the image.

Suppose we use the following code to add a watermark to the image:

 function addWatermark($imagePath, $watermarkText) {
    $image = imagecreatefromjpeg($imagePath);
    $textColor = imagecolorallocate($image, 255, 255, 255); // Set the watermark text color to white
    $fontPath = "path/to/font.ttf"; // Font file path
    $fontSize = 20;

    // Add watermark to the bottom right corner of the image
    imagettftext($image, $fontSize, 0, 10, imagesy($image) - 10, $textColor, $fontPath, $watermarkText);

    imagejpeg($image, "watermarked_image.jpg");
    imagedestroy($image);
}

addWatermark("image.jpg", "Sample Watermark");

This code will add a watermark text "Sample Watermark" to the lower right corner of the image. Next, we discuss the effect of executing the imageflip() function after adding a watermark.

3. Imageflip() flip effect after adding watermark

3.1 Differences before and after horizontal flip

When we perform horizontal flips after we add a watermark to the image, the effect of flip changes a little. When flipped, the position of the watermark will also be flipped horizontally. If the watermark is originally located in the lower right corner of the image, after being flipped horizontally, the watermark will move to the lower left corner.

 $image = imagecreatefromjpeg("watermarked_image.jpg");
imageflip($image, IMG_FLIP_HORIZONTAL);
imagejpeg($image, "flipped_watermarked_image.jpg");
imagedestroy($image);

At this time, the watermark will be flipped from the lower right corner to the lower left corner, showing the same effect as the image content flip.

3.2 Differences before and after vertical flip

Similarly, when vertical flip is performed, vertical flips of the watermark position will also occur. If the watermark is in the lower right corner of the image, it will be moved to the upper right corner after being flipped vertically.

 $image = imagecreatefromjpeg("watermarked_image.jpg");
imageflip($image, IMG_FLIP_VERTICAL);
imagejpeg($image, "flipped_watermarked_image.jpg");
imagedestroy($image);

This flip effect will make the watermark appear "inverted", but its relative position will always be consistent with the flip of the image content.

3.3 The effect of horizontal and vertical flips simultaneously

If the image is flipped horizontally and vertically at the same time, the watermark position will be restored to its original position. For example, the watermark originally located in the lower right corner will return to the lower right corner after performing horizontal and vertical flips.

 $image = imagecreatefromjpeg("watermarked_image.jpg");
imageflip($image, IMG_FLIP_BOTH);
imagejpeg($image, "flipped_both_watermarked_image.jpg");
imagedestroy($image);

In this case, the watermark seems to have not changed, but in fact, it is synchronized with the image flip operation.

4. Summary

When you flip an image using the imageflip() function in PHP, the position of the watermark changes with the flip. Whether it is flipping horizontally, vertically, or doing both at the same time, the watermark will be adjusted as the image is flipping. Understanding this can help developers better control the effects of image processing and ensure that the watermarks are always displayed on the image in the expected way.

5. Things to note

The font, color, size and other parameters of the watermark can be adjusted according to needs.
When using watermarks, you need to pay attention to whether the watermark text or image is too obvious, which may affect the aesthetics of the image.
In actual use, the image after imageflip() operation should be saved and output in time.

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