I'd like to create a responsive SVG that consists of an image clipped by a polygon.
The image needs to preserve its aspect ratio and get cropped, while the polygon needs to adapt in width to its container but preserve the same height.
I don't want the whole thing to scale homothetically.
visual explanation of the issue
If I set preserveAspectRatio="none" to the svg, the polygon stretches like planned, but the image is then distorted. I've tried setting preserveAspectRatio="xMidYmid slice" to the image, but since the svg is set not to have its aspect ratio preserved it doesn't work as planned.
Here's my current code:
<svg viewBox="0 0 1440 810" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<clipPath id="clip">
<polygon points="0 750,1440 810,1440 60,0 0" />
</clipPath>
</defs>
<g aria-hidden="true" clip-path="url(#clip)">
<image
opacity="0.75"
preserveAspectRatio="xMinYMid slice"
xlink:href="https://upload.wikimedia.org/wikipedia/commons/thumb/6/6e/Monasterio_Khor_Virap%2C_Armenia%2C_2016-10-01%2C_DD_25.jpg/2880px-Monasterio_Khor_Virap%2C_Armenia%2C_2016-10-01%2C_DD_25.jpg"
/>
</g>
</svg>
Thanks in advance for your help.
I'm working on a PHP script that generates a jpg wallpaper from an SVG-file according to the screen resolution of the visitor. The wallpaper consists of a circular gradient (rectangle) background and a path on top of it. How would you go about centering the path horizontally and vertically to the rectangle? Remember that the rectangle's size and proportions are not a constant. Should I separate the background and path to different svg files or is there an easy way to center paths? Maybe a framework?
This is easilly achieved by using nested <svg> elements and the preserveAspectRatio attribute. Put your background in the outer svg and your path in the inner one.
<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="100%" height="100%">
<rect id="background" width="100%" height="100%" fill="grey"/>
<svg preserveAspectRatio="xMidYMid meet" viewBox="0 0 30 40" width="100%" height="100%">
<g>
<circle cx="15" cy="20" r="10" fill="yellow"/>
<circle cx="12" cy="17" r="1.5" fill="black"/>
<circle cx="18" cy="17" r="1.5" fill="black"/>
<path d="M 10 23 A 8 13 0 0 0 20 23" stroke="black" stroke-width="2" fill="none"/>
</g>
</svg>
</svg>
Run this snippet and try resizing the window.
To get this to work, all you need to ensure is that the viewBox attribute on the inner <svg> element is correctly set.
If you know the coordinates of the paths, you could take the total of the x/y coordinates and divide by the number of coordinates, this will give you the average position for the coordinate set. Then, offset each coordinate by the coordinates for half the width/height of the square, plus any offset, minus the difference between the center of the coordinate set and half the width/height of the square.
This should result in your coordinates being centered within the square, I think (it is rather early here, and I've just started my first coffee, so I could be wrong). This is of course assuming you know all the variables in play (the width/height of the square, any offset applied and the coordinates of the path).
Below is a screen capture of SVG image which is rendered on Chrome 22.0.1229.79 Mac. The original svg is on jsfiddle:
http://jsfiddle.net/LGBk5/
The left image is made using SVG:s dilate and erode filters. The right one is made using Illustrator's Offset Path effect.
The left one has problems: the border at the bottom is distorted and curves are not as smooth. Meanwhile the thick black border is the same in both.
Has my SVG some parameter wrong or are the dilate and erode filters so seemingly buggy?
EDIT: The purpose is to make paths thinner or thicker in SVG, but according to this example, the erode/dilate is not stable enough to rely.
Filter effects are done on pixel data (the rasterized path), while the path offset operation in Illustrator (similar in Inkscape) is done using the original path data (or vector data if you wish).
The former is like using photoshop filters, the latter is creating new paths by using the existing path. They're both stable, but they're not the same operation.
Illustrator's path offset and SVG filters erode/dilate are different operations.
This erode filter is working as designed - there is no bug here. For every pixel in the input image, the filter looks at the maximum RGBA values in a rectangle around it (the radius). In a normal image this tends to generate "rectangular highlights" for want of a better term. And results in weird artifacts when applied to curved draw paths. From the spec:
The dilation (or erosion) kernel is a rectangle with a width of
2*x-radius and a height of 2*y-radius. In dilation, the output pixel
is the individual component-wise maximum of the corresponding R,G,B,A
values in the input image's kernel rectangle. In erosion, the output
pixel is the individual component-wise minimum of the corresponding
R,G,B,A values in the input image's kernel rectangle.
So, imagine that that single pixel at the pointy end of your shape. With a 10 pixel "radius" in your filter (and remember that radius is an incredibly misleading term because it's using a rectangle not a circle!). Let's say it's at 100,100, for arguments sake. When the filter processes values for pixels in the range 90,110 to 110,110, its dilation radius is going to detect that pixel at 100,100 and paint all pixels in that range black. And just like that, your nice pointy end has been dilated into a straight line.
Note that you can achieve most offset path effects using nested strokes (some of which have masks to trim the inside or outside of the path.
For example, here is the OP's path reimplemented this way:
<!-- Left drawing is made using erode and dilate -->
<!-- Right one is made by Illustrator's Offset Path -->
<svg width="612" height="792" viewBox="0 0 612 792" xmlns="http://www.w3.org/2000/svg">
<defs>
<path id="curve" d="M21.552,74.438c2.531-28.879,73.668-52.734,102.629-53.971
c32.164-1.373,74.764,23.746,61.766,53.197c-32,72.5-84.236-59.594-109.5-29.5c-23.367,27.833,55.4,142.969,55.4,142.969
S18.109,113.708,21.552,74.438z"/>
<mask id="inner">
<use xlink:href="#curve" fill="white"/>
</mask>
</defs>
<!-- this black outermost line -->
<use x="10" y="10" xlink:href="#curve" style="stroke:black;stroke-width:26;stroke-linejoin:miter;stroke-miterlimit:10"></use>
<!-- thick red outer line -->
<use x="10" y="10" xlink:href="#curve" style="stroke:#f00;stroke-width:24;stroke-linejoin:miter;stroke-miterlimit:10"></use>
<!-- innermost black thin line, with green fill -->
<use x="10" y="10" xlink:href="#curve" style="fill:#1CFF00;stroke:black;stroke-width:32;stroke-linejoin:miter;stroke-miterlimit:10" mask="url(#inner)"></use>
<!-- blue inner stroke -->
<use x="10" y="10" xlink:href="#curve" style="fill:none;stroke:#5555FF;stroke-width:30;stroke-linejoin:miter;stroke-miterlimit:10" mask="url(#inner)"></use>
<!-- lastly, the black line -->
<use x="10" y="10" xlink:href="#curve" style="fill:none;stroke:black;stroke-width:10;stroke-linejoin:miter;stroke-miterlimit:10"></use>
<g transform="translate(210,10)">
<path fill="#FF0000" stroke="#231F20" d="M126.273,201.917c-1.188-0.766-29.407-19.044-57.679-42.532c-41.739-34.676-60.31-60.754-58.441-82.068
c1.575-17.974,18.042-34.105,48.943-47.945c21.673-9.707,48.782-16.997,65.925-17.729c1.023-0.043,2.057-0.065,3.096-0.065
c26.722,0,55.103,13.789,67.484,32.787c7.866,12.07,9.101,25.736,3.476,38.482c-8.697,19.704-20.608,29.697-35.403,29.702
c-0.002,0-0.007,0-0.01,0C144.382,112.551,127.62,95,111.407,78.028c-7.054-7.385-18.575-19.446-23.912-21.338
c-1.086,2.002-6.186,15.821,20.666,67.477c16.226,31.214,35.475,59.438,35.668,59.72l35.977,52.589L126.273,201.917z"/>
<path fill="#5555FF" stroke="#231F20" stroke-width="10" stroke-miterlimit="10" d="M22.939,78.438
c2.531-28.879,73.668-52.734,102.629-53.971c32.164-1.373,74.764,23.746,61.766,53.197c-32,72.5-84.237-59.594-109.5-29.5
c-23.366,27.833,55.401,142.969,55.401,142.969S19.497,117.709,22.939,78.438z"/>
<path fill="#00FF00" stroke="#231F20" d="M79.986,131.678C38.498,95.796,38.41,81.397,38.549,79.807c0.289-3.29,5.843-10.151,19.371-17.933
C57.676,78.899,64.972,101.816,79.986,131.678L79.986,131.678z M163.665,84.044c-7.09,0-22.461-16.091-31.646-25.706
c-5.867-6.143-11.433-11.969-16.966-16.846c4.324-0.776,8.128-1.238,11.184-1.368c0.621-0.027,1.249-0.04,1.88-0.04
c16.911,0,36.471,8.903,43.603,19.846c3.317,5.089,2.508,8.623,1.278,11.408C168.884,80.659,165.163,84.043,163.665,84.044
L163.665,84.044z"/>
</g>
</svg>
I would like to be able to set the stroke-width on an SVG element to be "pixel-aware", that is always be 1px wide regardless of the current scaling transformations applied. I am aware that this may well be impossible, since the whole point of SVG is to be pixel independent.
Context follows:
I have an SVG element with its viewBox and preserveAspectRatio attributes set. It looks something like this
<svg version="1.1" baseProfile="full"
viewBox="-100 -100 200 200" preserveAspectRatio="xMidYMid meet"
xmlns="http://www.w3.org/2000/svg" >
</svg>
This means that when I scale that element, the actual shapes inside it scale accordingly (so far so good).
As you can see, I have set up the viewBox so that the origin is in the center. I would like to draw an x- and a y-axis within that element, which I do thus:
<line x1="-1000" x2="1000" y1="0" y2="0" />
Again, this works fine. Ideally, though, this axis would always be only 1px wide. I have no interest in the axes getting fatter when i scale the parent svg element.
So am I screwed?
You can use the vector-effect property set to non-scaling-stroke, see the docs. Another way is to use transform(ref).
That will work in browsers that support those parts from SVG Tiny 1.2, for example Opera 10. The fallback includes writing a small script to do the same, basically inverting the CTM and applying it on the elements that shouldn't scale.
If you want sharper lines you can also disable antialiasing (shape-rendering=optimizeSpeed or shape-rendering=crispEdges) and/or play with the positioning.
Here is a more concise answer based on Erik's answer to help you get started quickly.
<div style="background: blue; width: 100%; height: 130px;">
<svg xml:id="root" viewBox="0 0 100 100" width="100%" height="100%" preserveAspectRatio="none">
<rect xml:id="r" vector-effect="non-scaling-stroke" x="0" y="0" width="100" height="100" fill="none" stroke="#88CE02"
stroke-linecap="square" stroke-width="10" stroke-miterlimit="30"/>
</svg>
</div>
Adding the vector-effect="non-scaling-stroke" to the SVG rect makes the border size (or stroke size) fixed.