Node.js GM channel() Function

Last Updated : 30 Mar, 2023

The channel() function is an inbuilt function in the GraphicsMagick library which is used to extract a particular channel from the image.

Syntax:

channel( channelType )

Parameters: This function accepts a single parameter channelType which holds the type of channel name. The types of channels are Red, Green, Blue, Opacity, Matte, Cyan, Magenta, Yellow, Black, or Gray.

Return Value: This function returns the GraphicsMagick object.

Example 1:

javascript

// Include gm library
const gm = require('gm');
 
// Import the image
gm('1.png')
 
// Invoke borderColor() function
// and set border color to green
.borderColor('Green')
 
// Invoke resize function
.border(10, 30)
 
// Invoke Channel function
// with 'All' parameter
.channel('All')
 
// Process and Write the image
.write("channel-all1.png", function (err) {
    if (!err) console.log('done');
});

Output:

Example 2:

javascript

// Include gm library
const gm = require('gm');
 
//Import the image
gm(600, 300, 'white')
 
// Set the color for the stroke
.stroke("green", 3)
 
// Set the font
.font("Helvetica.ttf", 60)
 
// Call to drawText Function
.drawText(100, 280, "GeeksforGeeks!")
 
// Invoke borderColor() function
// and set border color to green
.borderColor("Green")
 
// Invoke border function
.border(62, 32)
 
// Invoke Channel function
// with 'All' parameter
.channel('Green')
 
// Process and write the image
.write("channel-green.png", function (err) {
    if (!err) console.log('done');
});