Lockscreen resolution / compression issues and false info


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  1. MrXBob

    MrXBob Member This Topic's Starter

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    I've tried a bunch of my own images as my lock screen, all set at what i've been told is the correct resolution, but they always come out looking pixelated, dull and blurry...

    The images look extremely crisp and bright when i preview them in the lock-screen selection area - but when saved, theres a huge difference in quality.

    The resolution which fits perfectly is 320x455, but pretty much everyone online says its 320x480 which I know to be wrong because you can see it clearly doesnt fit the screen when you're selecting it - and so it gets resized up.

    I've tried JPG, PNG, TIF... I've tried different sample rates, different colour pallettes - nothing works.

    Even using the default HTC one (which looked gorgeous originally) - whenever I apply it now, it looks like it went through some 60% JPG compression... artifacts all over the place.

    Somebody help please :confused::confused::eek:
     

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  2. Ziani

    Ziani Well-Known Member

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    320x480 is the correct size, is what I use with no problem.

    When you have selected your image drag the box to full size, if you leave it it will crop.
     
  3. daveybaby

    daveybaby Well-Known Member

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    Yeah 320x480 is the actual screen resolution. However, i've found i get the best results by using a high resolution image and letting the phone handle the scaling. Same for homescreen wallpapers.

    Also bear in mind that the hero's screen is only 64k colours. This means that jpeg artifacts can actually be more visible than they would on a 16M colour display - artifacts that would normally be very close to the background colour and thus nearly invisible can get enhanced due to quantisation.

    So, for some images the artifacts are already there, they just stand out more on the hero's screen.
     
  4. MrXBob

    MrXBob Member This Topic's Starter

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    That's my point though - they don't show up until it's actually being used as the lock screen image. When I'm dragging the box to select the area, you can see that the image is 100% perfect. Save it and it goes to hell...

    Also I'm still not convinced that 320x480 is the screens correct resolution - if this were the case, images of that size would not show on the screen with grey borders down the left and right side, and I would be able to crop the entire image... yet dragging the box to fit the image always leaves off a section of either the top or bottom.

    320x480 is not the Hero's resolution.. cannot be :confused:
     
  5. Xyro

    Xyro 4 8 15 16 23 42 Moderator

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    It is the correct resolution; taking screenshots of the phone makes a 320 x 480 image. An image that size would get grey boxes at the side because you've only got 455 pixels of screen to display a 480 image in because of the notification bar.

    I use 320 x 455 .pngs and I haven't had any problems. It's really odd that there are no problems with yours untill you view them as the lock screen :S
     
  6. MrXBob

    MrXBob Member This Topic's Starter

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    So basically the image for the lock screen should not be 320x488 - it should be 320x455 like I said, because it shows directly below the notification bar rather than behind it..

    Either way, 320x455 PNGs end up looking a bit pants too.. the phone is obviously doing something to the image when it saves it :(

    Is there an app that will let me screenshot the lock screen?
     
  7. Slug

    Slug Check six! Moderator

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    Just so as I understand, you are dragging the crop box outwards so that it encompasses the entire image before hitting "Save"?

    If so, I dunno.... 320x455 is the correct res for lockscreens on the Hero. I've had no issues using 24/32bit JPGs - in fact I cropped a couple of 640x480 wallpapers last night to use as matching lock screens and they're fine.
     
  8. MrXBob

    MrXBob Member This Topic's Starter

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    I'm dragging the box right out as far as it goes, yes. I just now tried an image which is double the size, dragged the box all the way out and saved it - same thing happened.
     
  9. daveybaby

    daveybaby Well-Known Member

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    You know what, youre right. I've just checked in a bit more detail and there are definitely a lot more artifacts in the wallpaper than in the source image.

    it's definitely the screen resolution, whether it's the resolution of the wallpaper image or not (taking into account the status bar) is another matter.

    Chances are that finding the 'correct' resolution will make no difference in any case. It's likely that the wallpaper selection algorithm performs the resize (and thus introduces the artifacts) regardless, even if the image is already the exact correct size. Simpler to code, simpler to test, innit.

    In theory an app could be written to manage this better (i.e. use a better quality jpeg compression ratio, and not resize if the image is already correct), but if there is an app out there that does this then good luck finding it in the marketplace amongst the sea of shitty wallpaper image packs masquerading as apps. ('wallpaper plus' is pretty good but only does the homescreen).

    Having said that, there's probably a reason they use a high compression ratio: memory. I'm not talking about storage/flash memory - i mean RAM. More free RAM = better performance, so why waste even a few tens of kilobytes storing an image at high quality when youre only going to see it for a few seconds before you drag it out of the way? Be nice to have a choice though.

    Other than that you'll have to choose a source image that doesnt generate such visible artifacts (it does vary greatly from image to image).
     
  10. lobug

    lobug Banned

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    I think that the way the picture is compressed makes it easier for the Hero to render out the picture of the slided down screen, or something..
     

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