[Interest] QML Image size vs sourceSize strange things

Alexander Dyagilev alervdvcw at gmail.com
Sat Mar 27 08:57:08 CET 2021


OK, thank you. We do use SVGs (but sometimes also PNGs).

However, these PNGs I was talking about in the original posting are 
files icons from system. I can't replace them with SVGs. :)


On 3/27/2021 9:51 AM, Nuno Santos wrote:
> I had the same problem with blurry images on retina displays. I ended 
> up creating a image component that inside was by default setting 
> source size for twice the width and height of the item size to have 
> good results on iOS screens.
>
> However......
>
> I have recently found that replacing the pngs for svgs has accelerated 
> the UI loading time from seconds to a snap!!!
>
> I have found this because I was not finding acceptable the time it 
> took to resize a window.
>
> I had to replace years of pngs into svgs but in the end it payed off.
>
> You should definitely consider moving to svgs.
>
> Best,
>
> -- 
> Nuno Santos
>
>> No dia 27/03/2021, às 03:17, Alexander Dyagilev <alervdvcw at gmail.com> 
>> escreveu:
>>
>> 
>>
>> 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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>>>
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>>> Software/Firmare Lead Amotus
>>>
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>>>
>>> <image007.png>
>>>
>>>
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