I added two things for my use additional to sabinayakcs changes (described below). Maybe it helps someone else too:

• The Zoom gets back to 1 right before a cropping is applied. In my case the image got wrong resolution if the zoom was set to some else value.

• I enabled the zoom to be less than 1. Was there any reason for not doing this?

My setup is as following:

• I initialise TUI with full image size, so cssMaxWidth and cssMaxHeight is set to a never reached value like 100.000
• This leads to a very big image and I usually only need to zoom out ( < 1).
• The image is scrollable with scrollbars which indicate where I am. The Pan feature you introduced didnt worked well for me since the drawing tool always draws when paning with shift + mouse.

The Zoom is done by a input, a 1:1 and a 100% button (html uses fomantic ui):

<div class="ui action input"  style='position: absolute;    bottom: 12px;    z-index: 99;    left: 5px;'> 
    <input type="number" id='tui-zoom-input' min="1" max='1000' value="100" oninput="if(this.value >= 1){imageEditor.setZoom( (this.value / 100), false);}"> 
    <button class="ui button" onclick="$('#tui-zoom-input').val(100); imageEditor.setZoom(1, true);">1:1</button> 
    <button class="ui button" onclick="setInitialZoom();">auto</button> 
</div> 

The function setInitialZoom() is also called after tui is initialized and sets the zoom to fit the window and scrolls to the center:

function setInitialZoom() { 
    let zoom = $('.tui-image-editor-wrap').height() / $('.tui-image-editor-size-wrap').height(); 
    let zoom2 = $('.tui-image-editor-wrap').width() / $('.tui-image-editor-size-wrap').width(); 
    if(zoom2 < zoom) { 
        zoom = zoom2; 
    } 
    zoom = zoom * 100; 
    zoom = Math.floor(zoom); 
    $('#tui-zoom-input').val(zoom); 
    zoom = zoom / 100; 
    imageEditor.setZoom(zoom, false); 
 
    function centerVertical(){//centralize vertical 
        var scrollableDivJ=$(".tui-image-editor-wrap"); 
        scrollableDivJ.scrollTop("1000000");//scroll to max 
        var scrollHeight=scrollableDivJ.prop("scrollHeight"); 
       var diff=(scrollHeight-scrollableDivJ.scrollTop())/2; 
       var middle=scrollHeight/2-diff; 
       scrollableDivJ.scrollTop(middle); 
    } 
 
    function centerHorizontal(){//centralize horizontal 
        var scrollableDivJ=$(".tui-image-editor-wrap"); 
        scrollableDivJ.scrollLeft("1000000");//scroll to max 
        var scrollWidth=scrollableDivJ.prop("scrollWidth"); 
        var diff=(scrollWidth-scrollableDivJ.scrollLeft())/2; 
        var middle=scrollWidth/2-diff; 
        scrollableDivJ.scrollLeft(middle); 
    } 
 
    centerVertical(); 
    centerHorizontal(); 
 
} 

If this makes sense, then it might be an idea to merge this into the zoom function itself. I haven't done this, because its referencing dom objects which aren't created by tui. Maybe this PR doesn't make that much sense to you at all, but I just thought I'll share my implementation.

---

sabinayakcs readme of his fork:

Fork of Tui-Image-Editor

npm install @sabinayakc/tui.image-editor

Added Functionalities

• Zoom
• Pan
• Undo/Redo Data
• Arrow Shape
• Resize

Zoom

setZoom(value: number, reset: boolean = false);

• value > 1 & value < n
• reset = true (resets zoom and transform)

Pan

• Listen to image panned event.

imageEditor.on(
    imagePanned: (pan) => { 
        if (pan.x) {
          //If Pan.X is true, this means the width of image is not inside pan boundary
        }
        if (pan.y) {
          //If Pan.Y is true, this means the height of image is not inside pan boundary
        }
      }
   );

• Hold Shift Key + Mouse Drag (Zoom must be greater than 1) to pan the image.

Undo/Redo Data

imageEditor.undo().then(undoData => console.log(undoData)); imageEditor.redo().then(redoData => console.log(redoData));

• Useful for updating UI to last redo or undo change.

Arrow Shape

• New arrow shape type. imageEditor.setDrawingShape('arrow');
• To create an arrow, click on the canvas to create the arrow orign and drag the mouse to where you want the arrow to point.

Resize

imageEditor.resize({width: 640, height : 480})

• Listen to image resized event imageEditor.on(imageResized: img => console.log('Resized image', img));