Safari mobile blurry when scale - javascript

i have a panel that should be drawn floating over the normal html page.
This object is dynamically created on DOMloaded event and scaled to fit current screen resolution depending on the zoom level of page.
In order to obtain that we have to scale the element, because we fix the width and height.
The scale amount in not mobile friendly website is always bigger than 1. It seems to work in all browsers except for Safari mobile, in which the floating panel is blurry.
How can i solve this problem?

It is the device, not the browser. iPhones have retina displays, which, in plain words, means that the pixels are doubled. Fonts, borders and other CSS styles scale up fine, but images are stretched, that's the reason your image appears blurred.
The simplest way to fix this is to use a bigger image
Of course this has the drawback that well... you will be using a bigger image for all devices/browsers even if you don't need one. Of course, there are many other ways to handle this.
Here is a place to start:
https://www.smashingmagazine.com/2012/08/towards-retina-web/
http://www.mightybytes.com/blog/make-retina-images-website/

Related

Zooming SVG is blury or pixelated, not sharp

vI know to some extent this is a known issue that has been asked here but never answered, but I'm hoping for some additional insight.
I have a simple SVG image in a div on a web page. I want to be able to zoom the image using pinch gestures and have the SVG render sharply. It doesn't need to be sharp during the zoom, but should be sharp after the gesture is complete.
I'm doing my testing on a Windows 8.1 computer with a touch monitor, on an iPad, and on an old Android Galaxy Tab. On the main computer, I'm using IE11 and Chrome. For handling touch gestures, I'm using Hammer.js. I'm doing the zooming by modifying the transform CSS using the jQuery css() function (I'm setting scale3d and translate3d).
IE11 on my computer works exactly like I would like it to. It keeps the SVG image sharp throughout the pinch zoom and the image is always sharp regardless of when I set the CSS.
Chrome on my computer always renders the SVG blocky when I am zoomed in using pinch zoom. It is blocky during the zoom and does not get sharp afterwards. If I add a call to zoom the image after the page (x13) is loaded, the image is sharp. If I use a setTimeout() call to reset the zoom and then rezoom the image after the pinch zoom ends, the image is sharp.
On the iPad and Android tablet, the SVG never renders sharply, regardless of when I zoom it in code.
Does anyone have any ideas of how to reliably end up with a sharp rendering of SVG after a pinch-zoom is completed? Does anyone have a better solution? Using the SVG viewBox to zoom and pan during the gesture does not provide good enough performance for our more complex SVG images. I'm thinking of attempting to use the hardware accelerated scale3d/translate3d during the gesture and then attempt to convert this to new SVG viewBox settings afterwards, but this is a challenge and I'm not sure panning will work correctly after this is done. Any pointers or ideas are greatly appreciated.
Having just tried to answer your other SVG Question I will have a try at this one.
Michael Mullany is spot on that GPU translations will never give you a sharp image. This is because the GPU just maps one array of pixels to a new one. Because it has no concept of lines or rectangles the resolution is set by the time the GPU gets the image. The CPU will always struggle to re-render in time for a smooth drag.
What happens to allow some browsers to produce a sharp image is they do clever manipulations like rendering more pixels than they need so some zooming can happen without loss of resolution. These however are completely inconsistent and just not possible to rely on.
The as I see it 'correct' solution is to translate and zoom with hardware accelerated transformations during a pinch or zoom and then to refresh the viewbox with no css transformation when the translation has finished.
Challenges to overcome are
The css transformation will use screen coordinates but the viewBox manipulation will use the SVG coordinate system.
There are browser inconsistencies in both screenCTM and device pixel ratio
limits so that people don't drag or zoom too far need to be calculated in both systems
Pinch centerpoints also need to be calculated in both
To improve performance further the css transforms will be wrapped into updating on the requestAnimationFrame loop.
My working solution is hammerhead2. I am concentrating on desktops and android mobiles first and it seams to be working for them. To simplify the problem zoom is always centered to the screen center. I do however thing this is currently one of the only solutions. Here is an example of it working.

Image stretches after JS image source change in Firefox

Scroll through the images in Firefox (tested on v. 26) and you notice if you look to the right that the image stretches one pixel (or so) after its .src has been changed. This behaviour only occurs in Firefox and if the width of the image is increased or decreased by 1px (through web console), the behaviour disappears... I know that the image is bigger than the width I set but it still doesn't explain the behaviour and why it's only occuring at a very specific width (after all, image is still resized in browser if I increase or decrease the width by 1px as well but then the behaviour disappears). Works perfect in Opera, Chome, Safari and IE...
http://www.mosaikdesign.se/galleri_.php
Anyone?
I spent some time researching this and they way I see it, it's a bug.
I filed a bug report at Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=953364
I also made a thorough test page for those interested in studying this behaviour: http://www.blackwinged-angel.com/bugs/index.html
And finally, the fix:
-Set css property image-rendering on the image to something else than auto (optimizequality, optimizespeed, -moz-crisp-edges). It's claimed in the documentation that optimizequality and optimizespeed are the same as auto (https://developer.mozilla.org/en-US/docs/Web/CSS/image-rendering) but they do result in different downscaling algorithms being used (see my link for proof). However, this fixes the problem.
-Use image sizes where images are only upscaled, not scaled at all or check the resulting downscaling since it only applies to certain sizes of the containing element in relation to certain actual image sizes, not all.
Again folks, this only applies to Firefox, was tested on Firefox 26, applies to downscaling images on-the-fly in the browser by styling img (and possibly other) elements with width and height and it's not consistent (just happens at about roughly 30% of tested downscalings on a specific image for me).

Detect if the viewport width is bigger than the visible width on Mobile Safari using javascript

I have an element with position fixed (pinned to any corner) on a page (which I do not necessarily have control over the meta viewport tag - it is an embedded widget for third party sites). On Mobile Safari when the user pinch zooms the page at a certain point the viewport becomes larger than the visible area. At that point the fixed position element stays attached to the viewport and is not necessarily in the visible area.
I would like to compare two widths: the width of the visible area and the width of the viewport. I believe the size of the visible area is window.innerWidth. I am not sure how to measure the viewport.
I have been trying to see the relationships between:
document.documentElement.clientWidth
screen.width
window.innerWidth
window.outerWidth
...But have not been able to see anything obvious.
This is butt ugly but it does show some code that almost works (view on iOS to see it working. Use a desktop and click edit at top right of page to see or edit code):
https://jsbin.com/jopamu (iOS only)
The trick with the "overzoom" calculation is nasty but it does compensate somewhat for the multiple viewport zooms. It is a complex problem to solve because there are competing issues:
pinch-zoom
zoom due to input focus
the "position:fixed" zoom
potentially the OS (accessibility) zoom
The possible solutions I have found are:
Position the menu using the calculations above and position:absolute - updating the left/top in onscroll event. Has ugly juddering (can improve a little by hiding and only showing when zooming/scrolling finishes).
Position the menu using position:fixed but change the left/top to correct the menu position as zooming/scrolling occurs. Much less judder but I couldn't quite get it 100% reliable (some race condition).
Not suitable for your case (and highly unrecommended due to risk of breaking things): you can prevent pinch zooming and iOS10 double-click zooming by cancelling default on touchstart. Difficult because it needs many other workarounds so normal touch works, and needs synthetic scrolling and zooming (but has ugly side effects such as preventing scrolling working sometimes and also interferes with accessability e.g. if voice accessability turned on etc etc).
If you just want to see the widths then use the older version:https://output.jsbin.com/jopamu/6

Sub Pixel CSS positioning

If I set the CSS position attributes of an image element to floating points via javascript, Firefox renders it nicely, but other browsers do not. Can I get sub pixel positioning to work with other browsers? I like to seamlessly zoom in on an image, without jittering due to my values getting rounded off. For example, it seems like 2.217px; becomes '2px;' in all browsers except for Firefox. This happens with setting the value via style.top or via style.webkit-transform: translate(x, y).
In the end, I've managed this by drawing the image on the HTML5 canvas element.

Web: solution for image rotate and zoom

I have a web page which displays a large image, for example a page from a magazine. I have no control over the image size or orientation. It's possible that the image may need to be rotated by the user to orient it correctly.
Are there any Javascript or Flash solutions that will allow someone to rotate and zoom a given image? Ideally I'd specify a single image and the dimensions to use when displaying it. If the image is larger than those dimensions, the user could zoom in and view a portion of the image in greater detail.
I've seen a couple of solutions for rotating images with straight Javascript and CSS. Raphael would do the trick. There is apparently even an example featuring rotating an image. (it uses SVG but is support on all major browsers)
This one is not cross browser, but is an interesting exercise nevertheless.
As for flash rotation etc...
For rotating images, I used jquery-rotate and it works very well.
It is not totally cross-browser, it doesn't work with IE6 (and probably other old browsers).
For zooming, I guess you could make your own implementation using javascript, you can just resize the image (easy with jQuery).

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