Memory Leak in Image

[hhelwich]

There is a memory leak in the current stable version of node-canvas.

Steps to Reproduce

1. Start some program to observe system memory
2. Run the following code in node (set url to some Jpg file):

const canvas = require('canvas');

const loadImageNTimes = n => {
    if (n > 0) {
        const image = new canvas.Image();
        image.onload = () => {
            // Uncomment the following line to free image memory:
            // image.src = '';
            loadImageNTimes(n - 1);
        };
        image.src = 'some.jpg'; // Set Url to an existing Jpg file
    }
};
loadImageNTimes(500);

3. You should see that the memory is now growing linearly
4. Uncomment the line image.src = '' and run the script again
5. The memory stays constant now

Environment:

• node-canvas 1.6.10
• node 9.11.1 on Ubuntu 17.10

[Hakerh400]

Listener image.onload is called synchronously when image.src becomes a valid file path. Therefore, old image data structures cannot be deallocated until the last image finishes loading. You can fix it by adding setTimeout inside onload event listener.

[hhelwich]

Oh i didn't expect that 😶 This solves the issue. Thank you!

[zbjornson]

This is also fixed by #1003 in 2.x.