[Question] calculate image size before display

[trumdongnat]

I am trying to show list of image from urls in collection view(one column). Image width is fit to screen width and the height is calculated base on the width and the aspect is preserved.

HeightRequest=screen width * original image height / original image width

Please let me ask 2 questions

1. How to get the original size of image.
2. How to set the HeightRequest before render/decode the image.

[jonathanpeppers]

Do you even need to know the size of the image here?

Can you just set:

• WidthRequest to screen width
• Center the image horizontally/vertically (need both in case the image is smaller than the screen)

[trumdongnat]

@jonathanpeppers sorry, the solution is not working for me.
I tried both Center and CenterAndExpand. If I don't set the HeightRequest, the height of Image will be about 1, 2 px. I think when the collection view calculate the size of Image, because the Image is still not loaded, the Image require only 1 px. And its size is not update again after finish loading.
So I think I have to set HeightRequest manually when It loaded.

[trumdongnat]

Update.
I found solution now.

1. How to get the original size of image.
   I follow this guide
   https://stackoverflow.com/questions/47827015/how-to-get-original-image-size-by-using-glide-on-android
2. How to set the HeightRequest before render/decode the image.
   I create ImageSizeContainer to contain the image size. When I get the original size, I add it to container.
   The container will raise the event with url and original size of image.
   The Image will listen the event and update HeightRequest.
   My list can scroll smoothly now.
   Thank you very for this project.