[forms-devel] Intent of Image.IsOpaque

[Christoffer Årstrand]

Yes, that is normally how it is handled.

However either the flag is named incorrectly (supposed to be hasAlpha or
something) or the documentation is wrong (negated). An image that is marked
“opaque” is not supposed to be treated as it was transparent…

So the question is valid, are you suposed to set it to false (naming) or
true (docs) for transparent images?

Cheers,

CHRISTOFFER ÅRSTRAND
DEVELOPMENT LEAD
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From:  forms-devel <forms-devel-bounces at lists.dot.net> on behalf of Jason
Smith via forms-devel <forms-devel at lists.dot.net>
Reply-To:  Jason Smith <jas at microsoft.com>
Date:  Tuesday 16 August 2016 at 09:24
To:  이승근 <hi.root at gmail.com>, "forms-devel at lists.dot.net"
<forms-devel at lists.dot.net>
Subject:  Re: [forms-devel] Intent of Image.IsOpaque

IsOpaque is really a performance optimization. It is safe for a backend to
ignore. A rendering engine can take certain shortcuts if it knows an image
is opaque. That is all.
 
From: forms-devel [mailto:forms-devel-bounces at lists.dot.net] On Behalf Of
???
Sent: Thursday, August 11, 2016 7:57 PM
To: forms-devel at lists.dot.net
Subject: [forms-devel] Intent of Image.IsOpaque
 
Hi, all

Who is known intent of Image.IsOpaque?

It only implemented in iOS, others platform renderers ignore this property.

Anyway, Currently Xamarin document describe this property like below
https://developer.xamarin.com/api/property/Xamarin.Forms.Image.IsOpaque/
<https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fdeveloper.
xamarin.com%2fapi%2fproperty%2fXamarin.Forms.Image.IsOpaque%2f&data=01%7c01%
7cjas%40microsoft.com%7c371abcf60fc24a65ae4008d3c25c457d%7c72f988bf86f141af9
1ab2d7cd011db47%7c1&sdata=Xx3kTYzcxzWU6N51CxryQKdyT17iKIcXnvtD5vPp%2f4M%3d>
"If true, you'll be able to see through transparent parts of the image."
According to this guide, If want show partially transparent image, IsOpaque
should be set true.
Is that right?

As I know, IsOpaque property was mapped iOS UIView.opaque
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIView
_Class/#//apple_ref/occ/instp/UIView/opaque
<https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fdeveloper.
apple.com%2flibrary%2fios%2fdocumentation%2fUIKit%2fReference%2fUIView_Class
%2f%23%2f%2fapple_ref%2focc%2finstp%2fUIView%2fopaque&data=01%7c01%7cjas%40m
icrosoft.com%7c371abcf60fc24a65ae4008d3c25c457d%7c72f988bf86f141af91ab2d7cd0
11db47%7c1&sdata=Ca%2fv7J0WSrIZ7tC9gBFLyzLfN0fcI4RSpttHEcLo30s%3d>
"You should always set the value of this property to NO if the view is fully
or partially transparent."
According to this guide, If want show partially transparent image, opaque
should be set false(NO)

Which is right?
Please, anyone answer this question.

Thanks!
Seungkeun Lee
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