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Pinch zoom in steps

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@JEE wrote:

Hi. This is a 'how to' question.

Scenario: I have a gojs canvas displaying an image. I control the 'zoom depth' that the user can select. I do this because I want to show different quality images at different zooms. So when you zoom 300% you are going to see an image that is actually 3 x the size of the 100% image. I do this so that at the set zoom steps there is no pixelation of the images. The scale of the gojs is never changed - I just change the image layer on show as the zoom increases. All works well with mouse-click and tap events to fire zoom process.

Question; I want to provide a familiar pinch-zoom facility on tablet. To do so I will need to listen for a pinch event and to know the delta on the pinch. And to do the stepping smoothly I will need to be able to do so during the pinch action. I can then relate the pinch delta to my pre-set images and expose as required.

So - what event should I be listening for and are there any examples you could link me to?

Thanks.

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