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' );
}); |
Output:
Reference: