Convert JPEG image files to WBMP image files with PHP

php editor Shinichi will introduce to you today how to use PHP to convert JPEG image files to WBMP image files. Both JPEG and WBMP are common picture formats, but in some cases, JPEG images need to be converted to WBMP format to achieve better display effects. Through PHP's GD library, we can easily implement this conversion process. Let's take a look at the specific steps!

Convert JPEG image files to WBMP image files

Introduction

JPEG (Joint Photographic Experts Group) and WBMP (Wireless Bitmap) are two widely used image file formats. JPEG is used to store high-quality photos and images, while WBMP is used to store simple black-and-white images, commonly used on mobile devices and e-paper displays. This article will guide you to convert JPEG image files to WBMP image files using php.

step

1. Install GD library

First, you need to install the GD library, which is a popular PHP image processing extension. You can install it via PECL using the following command:

pecl install gd

2. Load and create images

Use the imagecreatefromjpeg() function to load the JPEG image file, and the imagecreate() function to create a new image to store the converted WBMP file.

$jpeg_image = imagecreatefromjpeg("image.jpeg");
$wbmp_image = imagecreate(imagesx($jpeg_image), imagesy($jpeg_image));

3. Convert color

JPEG images use color blending modes, while WBMP images only use black and white. Therefore, you need to convert every pixel of the JPEG image to black and white.

The following PHP code uses the imagecolorallocate() function to define color IDs for black and white:

$black = imagecolorallocate($wbmp_image, 0, 0, 0);
$white = imagecolorallocate($wbmp_image, 255, 255, 255);

Then, use the imagecopymerge() function to copy each JPEG pixel to the WBMP image and overwrite it with the appropriate color ID:

for ($x = 0; $x < imagesx($jpeg_image); $x ) {
for ($y = 0; $y < imagesy($jpeg_image); $y ) {
$color = imagecolorat($jpeg_image, $x, $y);
if ($color > 0) {
imagesetpixel($wbmp_image, $x, $y, $black);
} else {
imagesetpixel($wbmp_image, $x, $y, $white);
}
}
}

4. Output WBMP image

Finally, use the imagewbmp() function to output the converted WBMP image to a file.

imagewbmp($wbmp_image, "output.wbmp");

Sample code

The following is a complete PHP code example for converting a JPEG image file to a WBMP image file:

Precautions

• WBMP images only support black and white, so the color information of JPEG images will be lost during the conversion process.
• WBMP image file sizes are typically smaller than JPEG files because they only store black and white pixels.
• When using the WBMP format, image quality may be degraded depending on the original complexity of the image.

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