Why do certain CSS matrix3ds fail to render - html

Problem: Certain values of matrix3d cause a div not to render at all, but the inspector's highlight area for the div is the correct shape.
I have an app which uses the camera to recognize four dots near the corners of a rectangular object. I calculate a matrix from the positions of those dots to map a div with a certain size to the quadrilateral defined by the screen positions of the dots. This is all fine, but at certain arrangements of the dots, the div being transformed by the matrix does not render at all. After implementing this, I found this example, which does much the same thing I'm doing, albeit without the AR: http://franklinta.com/2014/09/08/computing-css-matrix3d-transforms/
If you inspect a div with such a matrix, the blue highlight has the correct shape, but the div doesn't render. It also seems not to calculate pointer events, otherwise the cursor style would be visible. If you run the following snippet, you should be able to inspect the div and highlight it to see the shape is ought to have.
.rect {
position:absolute;
left:0;
top:0;
width:736px;
height:414px;
transform-origin:0 0;
background:red;
cursor:crosshair;
}
<div class="rect" style="transform:matrix3d(0.009359283667, 0.010930981398, 0, 0.000104500516, -0.092142538522, -0.121434733223, 0, -0.000225136056, 0, 0, 1, 0, -21.813928384019, -10.640940675131, 0, -0.106409406751)"></div>
<div>Inspect my invisible sibling...</div>
I'm currently using .toFixed(12) on each element of the matrix after calculation and right before applying it to the div. In my prior research to solve this, it was suggested that it could be a precision problem, but that doesn't seem to be the case. I have tried down to .toFixed(6), but that served only to make the matrix less correct.
I see this in Chrome, Version 42.0.2311.135 (64-bit) and Safari Version 7.1.5 (9537.85.14.17). I haven't tried other browsers.
Now, Frank Ta's example doesn't seem to have the same problem as mine, so I suspect there is some way I could calculate the matrices differently such that they would render correctly. However, that's not relevant to what I'm asking. My question is this: Why do these certain matrices cause normal rendering to fail, but highlighting them in the inspector shows the expected shape?
I can give a list of additional examples of such matrices if it would help.

Related

Misalignment of image and gradient border

For a web application, I need to display small images as a circle and draw a circular gradient-filled border around them using only HTML and CSS. For unknown reasons, some systems reproducibly show misalignment between the image and the border so that they are not concentric. On affected systems, this behavior is visible in both Chrome, Firefox, and Edge, however, the direction of the misalignment is different. Other systems, however, are perfectly fine.
Enlarged screenshot of the misalignment in my web application:
My first thought was, that this might be a subpixel rendering issue but since I am using an even-numbered image size of 24x24px and an even-numbered border width of 2px this seems unlikely. I did some experiments by gradually increasing the image size by 1px and found that the direction and extent of misalignment are inconsistent and sometimes there seems to be an oval distortion. Below you find a reduced code snippet at screenshots from Chrome, Firefox, and Edge. I indicated the direction of misalignment in red. Increasing the border width yielded similar results, but the effect seems most pronounced with 2px.
.rounded-corners-gradient-borders {
box-sizing: border-box;
padding: 2px;
border-radius: 100%;
background: linear-gradient(45deg, #F48ACE 0%, #493A97 100%);
}
<img class="rounded-corners-gradient-borders" src="https://i.picsum.photos/id/368/24/24.jpg?hmac=qTESgqsVn81m_y-i5SDjG0xncWcyf-gYC40Jw9amc-k" />
https://codepen.io/grilly17/pen/VwXNrMO
Annotated screenshot of Codepen output in Firefox:
Annotated screenshot of Codepen output in Chrome:
I am aware that drawing a perfectly concentric "solid colored" border can be achieved a lot easier, but the gradient is a hard requirement in this case.
Since it doesn't seem to affect all systems, I asked friends and colleagues to have a look at different OS types, OS versions, browsers, browser versions, monitors, screen resolutions, and different compute hardware but I was not able to find a common cause for this. The direction and extent of misalignment seemed to be different on every system and browser but it does not change when reloading the page in the same browser again. So it appears to be deterministic.
At this point, my best guess is that it is related to some rounding error in the rendering process, but I would love to get to the bottom of this. Does anybody know why this is happening at all and why it is only affecting some systems? Is there a better solution to achieve this?
Thanks to the hint of "CSS pixels vs screen pixels" I was able to understand the root cause and find a solution to my problem. I should have realized that the screenshot of the icon was 35px high instead of the expected 28px including padding.
Most OS have a display setting for "scaling" up everything on your screen by a certain factor, e.g. 125%. This affects everything on your screen and may cause fractional pixel values, which results in the effect described above. If you have multiple screens, the value might be different on every screen. For web applications, the active screen's scaling value is applied only on page loading/rendering and not when moving the page between screens.
The scaling factor can be accessed via the JavaScript window property window.devicePixelRatio.
Using this I was able to work out two acceptable solutions, which might be useful for others:
Get a "device pixel perfect" representation by undoing the scaling
Get a "no subpixel" representation by accounting for pixel fractions in the unscaled value
The enlarged screenshot below shows from left to right the original misaligned image, the "device pixel perfect" image, and the "no subpixel" image when using a display scaling of 125%.
Here is my code (tested on FF, Chrome, Edge): https://codepen.io/grilly17/pen/QWmegPj
function precompensateScaling(value, scale) {
return value / scale;
}
function precompensatePixelFractions(value, scale) {
return value - value * scale % 1 / scale;
}
// wait until page is fully loaded
window.onload = (event) => {
const original = document.getElementById('original');
const oHeight = parseFloat(window.getComputedStyle(original).getPropertyValue('height'));
const oPadding = parseFloat(window.getComputedStyle(original).getPropertyValue('padding'));
const scale = window.devicePixelRatio;
const unscaled = document.getElementById('unscaled');
//unscaled.style.transform = `scale(${1/scale})`; // alternative
unscaled.style.height = `${precompensateScaling(oHeight, scale)}px`;
unscaled.style.padding = `${precompensateScaling(oPadding, scale)}px`;
const adjusted = document.getElementById('adjusted');
adjusted.style.height = `${precompensatePixelFractions(oHeight, scale)}px`;
adjusted.style.padding = `${precompensatePixelFractions(oPadding, scale)}px`;
};
Thank you all for your support. I <3 the Stack Overflow community!

"destination-out"-like blending behavior using CSS?

I have an image. I have a second graphical element ontop of this image, whose alpha I want to use to "hide" parts of the image below it, while the top element itself isn't shown.
Something along the lines of
CanvasRenderingContext2D.globalCompositeOperation = "destination-out"
This top element will change transparency and shape live, so prerendering everything onto a seperate canvas won't be an option.
I was thinking of "multiply" but it didn't do what I expected it to. I thought if I put the alpha of the top layer to "0", that would be multiplied with the layer below, also making it transparent. (I was sad it didn't work)
Is there someway to "hack" this using the existing CSS blending modes (or any other method)?
As an alternative, consider mask-image (however, note that currently there's no support for this on IE / Edge):
img {
-webkit-mask-image: url(http://www.lordtennyson.ca/uploads/1/2/4/2/12421219/paw_print_small.png);
mask-image: url(http://www.lordtennyson.ca/uploads/1/2/4/2/12421219/paw_print_small.png);
}
<img src="http://www.dizzydi.com/uploads/6/5/6/5/65656887/6168555.jpg" />

SciChart - Accurate placement of rotated axis labels

Following up on my question from yesterday:
SciChart - showing labels for all ticks
Thanks to the answer I was able to get the label density where I needed it. But I still have problems with label placement. As you can see in the screenshot, rotating the labels caused them to stick upwards into the graph. I need them below the axis. I've tried everything I could find in the API that I thought might help me:
a TranslateTransform - I tried moving both X and Y both ways. No
result.
VerticalAnchorPoint and HorizontalAnchorPoint - setting
VerticalAnchorPoint to Center actually moved the labels, but only by
3mm and in the wrong direction.
Horizontal/Vertical
Alignment/ContentAlignment - didn't do anything.
I've even tried
bloating the labels by appending a lot of spaces to the strings. A desperate attempt, I know.
Furthermore, the horizontal position of the labels is not correct either. In the screenshot you can see the first bump on the graph goes down on what looks like CF.02. But in reality it's set to CF.01. It would seem the labels are moved to the left of their corresponding tick. I need them to be displayed below the center of their respective tick, like the original solution.
[edit: image removed to prevent potential client IP issues]
In the SciChart's WPF Xaml Styling a Chart example there is a demonstration of how to rotate labels by changing the AxisBase.TickLabelStyle.
This uses RenderTransform to rotate labels by 15 degrees. However, if you use 90 degrees, the labels overlap the surface.
Changing the RenderTransform to LayoutTransform forces labels to be drawn in the correct place (below the axis).
You can read more about the difference between RenderTransform and LayoutTransform here.

Strange difference between HTML and SVG span rendering in Safari

This question is a little specific and I am hoping someone here can shed some light on a potential solution for me.
All of the following points are important:
I am writing some HTML pages that are going to be read on a third party hand-held device.
In order to fit the requirements of this device each word must be in a separate span, this is for an upcoming feature of the device that I am not allowed to go into, but it has to be formatted like this.
This HTML is being converted from SVG, the SVG is created from Adobe Illustrator documents.
The only place I have any control of the creation of the HTML is in the conversion from SVG to HTML.
My problem is this, in SVG text is broken down into "text" nodes and tspan nodes. Look at this simple SVG, note how I am changing the Y coord on the first tspan.
<text><tspan y="50">Hello</tspan><tspan> World</tspan></text>
When this renders in a webkit based browser, like safari, the sentence "Hello World" is displayed with the word "World" right next to the word "Hello".
In my converted HTML example:
<div><span style="position:absolute;top:50px;">Hello</span><span> World</span></div>
"Hello" is displayed with a y offset of 50, however "World" is displayed in the top left corner origin of the page.
This is frustrating as I do not have the coords of where the "World" span should be placed in the SVG (as Illustrator does not need this coord to render it correctly). Also, there may be one or more tspans in the SVG with altered positions which will prevent me from applying the style to the div.
In short, does anyone know if there is an attribute I can set to place the second span directly after the first?
Thanks
You could style the div instead of the span
<div style="position:absolute;top=50px;"><span>Hello</span><span> World</span></div>
That would keep text-chunks together and positioned relative to each other, but you could still have a span for every single word
Have figured this out after trying a bunch of different things.
It is actually very straightforward, however I didn't realise spans could be nested so I am going to let myself off.
<div><span style="position:absolute;top:50px;"><span>Hello</span><span> World</span></span></div>
The trick is to wrap all the words that need to be grouped together in a span. Hopefully this helps anyone who is stuck on a similar issue.

CSS3 Transforms -- Alternate Trigger?

Usless Background Info
Hello, all. This is my first post here, but I often come here for help.
I am an amateur web designer and have been in web designing for almost a year now.
The Problem
My question is about CSS3 transforms. I have a small, circular element in the center of my page that transforms successfully when I hover over it. I have a larger circular element that is, by z-index, underneath it. The larger circle also has CSS3 transforms coded in the CSS, but will not transform, or even triggerd when hovered over. Both circles are overlaid, with the smallest on top, to create concentric circles.
My Attempted Solution
One word: Z-index. I have tried putting the larger circle on top, which works fine. The problem with this is that the smaller circle no longer triggers...
The Result I Want
I would like for the circles to remain in their 'concentric' positions and for the larger circle on the outside to transform by :hover. Is it possible to have an 'alternate trigger'? e.g.: in JavaScript, I can trigger an animation by hovering over any element that I specify. Is this possible to do in CSS? Can I hover element (I), and change properties for element (II)? If I cannot do this, how would I go about triggering animations for both circles, by hovering over only one? I am trying to stay with pure CSS/HTML, but I will accept JavaScript answers.
Last Notes
I hope I have provided ample info for a decent answer... Here is a screenshot: http://i.stack.imgur.com/WPj62.png
The circle with the infinity sign is the smaller circle element. The larger circle with the faint border around the screen is the other element.
EDIT:
Something's still not right, please take a look at the full code posted here: http://cssdesk.com/eJ8BH
If I understand your question, it sounds like when you hover over the small circle, you want both the large and small circle to transform, correct?
The easiest way is likely to use javascript for this. If you are using jQuery, it's even easier:
$('.littleCircle')
.hover(function(){
$(this).addClass('myTransformationClass');
$('.biggerCircle').addClass('myTransformationClass');
})
UPDATE: Some further examples based on follow-up feedback.
Here's what I'd do. First, give all 4 related elements a class so you can grab them via jQuery. For the example I use .rolloverSet
// grab all 4 elements and cache them
$rolloverSet = $('.rolloverSet');
// grab the one element that needs to have two classes
$otherElement = $rolloverSet.find('.otherElement');
$rolloverSet
.hover(function(){ // we'll add a hover event to each element in the group
$(this).addClass('myTransformationClass');
$otherElement.addClass('myOtherTransformationClass');
})
.blur(function(){ // remove the classes on mousout
$(this).removeClass('myTransformationClass');
$otherElement.removeClass('myOtherTransformationClass');
})
You do not need jQuery for this. You need to apply :hover on the parent element of the concentric circles and then apply the animation to its immediate children like this: http://jsfiddle.net/nimbu/taqr4/
Things I changed:
Updated to use shorter transitions, animations property
Added moz, o, unprefixed properties
Removed -webkit- from border-radius
Gathered common properties of concentric circles to prevent repetition
Fixed incorrect background-color (#00000000)