[Interest] QML Image size vs sourceSize strange things

[Alexander Dyagilev]

This all is not about my question in any matter. I do not care about SVG 
at all. And SVG are not used in this example.

Please learn to read question before answering....

On 3/23/2021 4:16 PM, Jérôme Godbout wrote:
> Do you really need to same memory by reducing the source size? I think 
> you should left the source size alone and sample the image from the 
> full source. Source size for SVG doesn’t make any sense, it’s 
> vectoriel, doesn’t have any size, it can scale to any dimension. When 
> playing with the image size (not the source) it will sample the source 
> for each pixel, not sure about the algorithm but you might need an 
> higher source resolution to get a proper image without artifact. I 
> would at least take the Screen.devicePixelRatio into the source size 
> into account and even add a x2 to ensure proper sampling, but I don’t 
> see any real advantage to play with the source size unless you really 
> are consuming way too much memory.
>
> This might slow you down if the same image is using different sourceSize:
>
> Note: /Changing this property dynamically causes the image source to 
> be reloaded, potentially even from the network, if it is not in the 
> disk cache./
> /
> /
>
>> On Mar 23, 2021, at 3:31 AM, Alexander Dyagilev <alervdvcw at gmail.com 
>> <mailto:alervdvcw at gmail.com>> wrote:
>>
>> Hello,
>>
>> We had a strange problem with blurred images under Retina displays. 
>> Left part of the image - before, right one - after the fix.
>>
>> <pjcgokflkeakcklh.png>
>>
>> Our QML code was using with to show images:
>>
>> Image{
>> anchors.verticalCenter:parent.verticalCenter
>> sourceSize.width:25
>> sourceSize.height:25
>> source:preview.url
>> }
>>
>> I've tried to multiply sourceSize by Screen.devicePixelRatio - images 
>> became bigger so they did not fit their places.
>>
>> Then I've replaced sourceSize.width with just width and the same for 
>> height. And it works fine now.
>>
>> My questions is:
>>
>> 1) Is it required to multiply sourceSize by devicePixelRatio? Or is 
>> it managed automatically? It seems that it is managed automatically 
>> for PNG and NOT managed for SVG.
>>
>> 2) If it is already managed automatically for PNG (these images 
>> preview.url are PNGs) then why was it blurred? The original PNG image 
>> is of size 64x64 pixels under Retina displays.
>>
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>
> Jerome Godbout
> Software/Firmare Lead Amotus
>
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