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Better quality downscaling of images
I've noticed that Opera does quite a poor job of downscaling images compared to all other browsers (despite beating them in almost every other department). Images that appear smooth in Chrome appear like little pixellated blobs in some cases.I think this matters because there are use-cases where a site wants to show a third-party image as a clickable thumbnail without having to process it manually or in PHP.
Has anyone else noticed this?
Originally posted by 50sQuiff:
Has anyone else noticed this?
No. A link would help a lot.
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It's particularly evident on detailed graphics like financial charts. Take this random chart I plucked off Google images: http://www.marketvolume.com/sbv/images/2009/20091113_sp500.gif
Now resize your browser down to 'thumbnail size' and compare the results in IE, FF, Chrome and Opera. All except Opera seem to apply a nice scaling algorithm.
Now resize your browser down to 'thumbnail size' and compare the results in IE, FF, Chrome and Opera. All except Opera seem to apply a nice scaling algorithm.
I haven't been able to spot any substantial difference while playing with the window size. Here's a screenshot where I tried to roughly match the respective window sizes for demonstrative purposes. Left Fx 8.0, right Opera 11.60.
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Make sure Interpolate Images is enabled. It is by default.
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6. December 2011, 21:57:24 (edited)
It occurs to me that it would be more useful to have that image on a HTML testcase page so the size can be precisely controlled. You should probably do this to make clear precisely what it is that you're seeing.
Something like this would probably suffice. Adjust the pixel value to whatever you need to show the problem as it occurs for you.
Edit: updated the testcase to be a little more comprehensive. Note that I don't notice any difference worth mentioning.
Run it here: http://files.myopera.com/Frenzie/files/test/image-resize-test.html
This is what it looks like for me.
It seems to me that on the smaller ones there's no real difference while on the 300px-wide screenshot Opera actually has some almost readable text which is completely illegible in Firefox. That'd be quite the opposite of the original claim. Check your settings and post a screenshot of the testcase please (or adjust it to widths that are more appropriate for showing the problem!).
Something like this would probably suffice. Adjust the pixel value to whatever you need to show the problem as it occurs for you.
<!DOCTYPE html>
<title>Image resizing test</title>
<style>
img{display:block}
img{width:100px}
img+img{width:150px}
img+img+img{width:200px}
img+img+img+img{width:300px}
</style>
<img src="http://www.marketvolume.com/sbv/images/2009/20091113_sp500.gif">
<img src="http://www.marketvolume.com/sbv/images/2009/20091113_sp500.gif">
<img src="http://www.marketvolume.com/sbv/images/2009/20091113_sp500.gif">
<img src="http://www.marketvolume.com/sbv/images/2009/20091113_sp500.gif">
Edit: updated the testcase to be a little more comprehensive. Note that I don't notice any difference worth mentioning.
Run it here: http://files.myopera.com/Frenzie/files/test/image-resize-test.html
This is what it looks like for me.
It seems to me that on the smaller ones there's no real difference while on the 300px-wide screenshot Opera actually has some almost readable text which is completely illegible in Firefox. That'd be quite the opposite of the original claim. Check your settings and post a screenshot of the testcase please (or adjust it to widths that are more appropriate for showing the problem!).
The DnD Sanctuary — a safety net for My Opera's demise.
Bad downscaling is especially noticeable with simple graphics (vectors and solid colours). Here's a quick example:
As you can see the image (4000x4000 original size) is downscaled perfectly in an external image viewer (IrfanView) and in Chrome. But it has jagged outlines in Opera, Firefox and IE.
As you can see the image (4000x4000 original size) is downscaled perfectly in an external image viewer (IrfanView) and in Chrome. But it has jagged outlines in Opera, Firefox and IE.
My primary thought is that in Irfanview you can choose between half a dozen (or even more) different algorithms for rescaling, some of which do well on drawings while others do well on (certain types of) photographs. There's also the matter of how computationally intense certain methods of rescaling are. But yes, for the screenshots as given (for the chart and the hello kitty) Chrome's method clearly looks best.
I added some JS to the testcase to make it slightly easier to play around with http://files.myopera.com/Frenzie/files/test/image-resize-test.html
I added some JS to the testcase to make it slightly easier to play around with http://files.myopera.com/Frenzie/files/test/image-resize-test.html
The DnD Sanctuary — a safety net for My Opera's demise.
I'm going to have to bump this since it looks like this problem finally got fixed in Firefox, leaving Opera the only modern browser with such poor downscaling.
https://bugzilla.mozilla.org/show_bug.cgi?id=486918
https://bugzilla.mozilla.org/show_bug.cgi?id=486918