Image Transparency Tool

Instructions

1. This tool simply lets you select a local image to view; the color of the first pixel (0, 0) is made transparent.
2. You can then save the now-transparent image to your PC.

Learning Notes

1. Despite the onchange in the INPUT tag, it still seems to require an event listener (for the document). (Both seem to be required.) I may be doing something wrong.
2. document.addEventListener(event, function, [useCapture]) → looks funny as a full function is taken as argument (including ; ). useCapture: false (default) = event during bubbling phase, true = during capturing phase (whatever that means).
3. Strangely, the file opening seems to be coded after the preview/using of it. But it still seems required to work.