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Nodejs | GM channel() Function
  • Last Updated : 14 Aug, 2020

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 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:






// Include gm library
var 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:




// Include gm library
var 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');
});

Output:

Reference:




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