How to convert photos into pixmaps with Nodejs

With the continuous advancement of technology and the development of the Internet, people's demand for pictures and videos on the Internet is getting higher and higher. For every programmer, we need to master some basic skills, such as photo conversion. Today, let’s talk about how to convert photos into pixel images using Nodejs.

First, let’s take a look at what a pixel image is. A pixel image is a picture composed of pixels, which means that a pixel image is a way of representing an image on a computer. It consists of the color and position of each pixel. Therefore, we can change the pixel map by manipulating the color and position of the pixel.

In Nodejs, we can use the Pngjs library to manipulate pixel images. Pngjs is a streaming PNG encoder/decoder that allows you to encode and decode PNG images using Nodejs, making it easier for developers working with JPEG and GIF.

First, we need to use Nodejs's fs (file system) module to read the photo, and then use the Pngjs library to convert the image into a PNG file. The sample code is as follows:

const fs = require('fs');
const PNG = require('pngjs').PNG;

const input = fs.createReadStream('image.jpg');
const output = fs.createWriteStream('image.png');

input.pipe(new PNG()).on('parsed', function() {
  this.pack().pipe(output);
});

In the above code, we use the createReadStream method to read the image, and then use the createWriteStream method to save the png file. Then, we use the new PNG() method to convert the image stream into a PNG file, and after the image parsing is completed, we create an output file stream and save it to the hard disk.

Next, we need to convert the image into a pixel image. In Pngjs, we can use the getPixel method to get the color of the pixel. The sample code is as follows:

const fs = require('fs');
const PNG = require('pngjs').PNG;

const input = fs.createReadStream('image.png');

input.pipe(new PNG()).on('parsed', function() {
  for (let y = 0; y < this.height; y++) {
    for (let x = 0; x < this.width; x++) {
      const idx = (this.width * y + x) << 2;

      // get the pixel color (R, G, B, A)
      const red = this.data[idx];
      const green = this.data[idx + 1];
      const blue = this.data[idx + 2];
      const alpha = this.data[idx + 3];

      // convert pixel color to another format
      // ...
    }
  }
});

In the above code, we use the getPixel method to get the color of each pixel, and then save it to the RGB (red, green, and blue) color space. We can perform any operation on the color of pixels in RGB space, such as adjusting brightness, contrast, hue, saturation, etc.

Finally, we use the pack() method in the Pngjs library to repack the pixels into a PNG image, and use the createWriteStream method to save it to the hard disk. The sample code is as follows:

const fs = require('fs');
const PNG = require('pngjs').PNG;

const input = fs.createReadStream('image.png');
const output = fs.createWriteStream('output.png');

input.pipe(new PNG()).on('parsed', function() {
  for (let y = 0; y < this.height; y++) {
    for (let x = 0; x < this.width; x++) {
      const idx = (this.width * y + x) << 2;

      // get the pixel color (R, G, B, A)
      const red = this.data[idx];
      const green = this.data[idx + 1];
      const blue = this.data[idx + 2];
      const alpha = this.data[idx + 3];

      // convert pixel color to another format
      // ...

      // set the pixel color (R, G, B, A)
      this.data[idx] = red;
      this.data[idx + 1] = green;
      this.data[idx + 2] = blue;
      this.data[idx + 3] = alpha;
    }
  }

  this.pack().pipe(output);
});

In the above code, we re-save the color of the pixels into the data and use the pack() method to repackage it into PNG format. Finally, we save it to the hard drive. Now, we have successfully converted photos into pixel art!

To summarize, we used the fs module of Nodejs to read the image data, and then used the Pngjs library to convert it into PNG format. Next, we use the getPixel method to get the color of each pixel, operate on it, and save it to the data again. Finally, we use the pack() method to repackage the data and save it to the hard disk using the fs module.

Through the introduction of this article, we can master how to use Nodejs to convert photos into pixel images, and also understand the basic usage of the Pngjs library. Whether you're developing a Nodejs application or something else, these tips will help you better manipulate and manipulate images.

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