Sorry, I am a beginner, sometimes i find people saying that I have to scale only the CSS, and the other examples i find that they multiply the size directly with the new scale, in other words canvas.width VS canvas.style.width
What is the difference?
Does latest Chrome behave like Safari (now in March 2014)?
Canvas consists of two parts: the element canvas which is what you see on screen. Then sort of "behind" the scenes there is the image bitmap which you draw onto.
Setting element.style will only affect the element itself, but not the behind the scene (internal) bitmap. This bitmap is simply stretched to fit the element size (like an image). If the size isn't specified it will default to 300 x 150 pixels.
The width and height properties (or attributes for the tag) are the ones setting the size of the internal bitmap.
An element without CSS will typically adopt to the size of the internal bitmap (there is pixel aspect ratio involved here as wel but normally the relationship is 1:1).
You can however override this by setting the element's CSS size. Again, it doesn't affect the internal bitmap but simply stretches it to fit the element.
All browsers should behave the same.
Related
I am trying to show a diagram of products with the image to scale. I have the image element sized with a width and min-width set to the correct width for the image.
I have an 'resize' event listener triggering my zoom on the image element to equal a correction factor:
const ratio = (window.innerWidth / window.outerWidth)
This works acceptably except when the browser vertical sidebar is open.
I searched here and could not find a property to show me sidebar width or to accurately detect zoom level in all browsers. I can use window.devicePixelRatio but that is not working in mac safari.
Would a canvas or svg element offer me some opportunities here i don't see?
Perhaps the best is just to have a input type='range' element next to the image to allow calibration to common object such as a credit card or coin.
Am I mistaken in thinking that if my picture is correct at 600px on my machine that it can be rendered universally in the browser with css width settings?
Thanks alot for any reflections
I am currently learning css and I have encountered some question about the SVG img. I have discovered that some SVG will take up the whole width of webpage if their width or height are not set, while some don’t and have a defined size. What does this property called? Is it related to the design of SVG image? example
Also, if I put a SVG which takes up the whole width of webpage into a flex box, the SVG will decrease in size. Why does this happen? Considing that a normal image and a SVG with defined size will not decrease the size in the same situation.example(fixed with class = "flex" instead of id).
I am also wondering how does the computer determine what size should the SVG decreased to? I have tried a few SVG(which take whole width) and almost each of them will decreased to a value near 150px x 150px in the flex box.
outer <svg> elements are replaced elements in CSS/HTML parlance and follow the rules for replaced element sizing
In particular if replaced elements have no defined size the browser falls back to a size of 300px x 150px, which is likely what you're seeing.
Normal i.e. raster images always have a defined size and are not replaced elements.
See also the SVG specification for how CSS affects SVG sizing
Following http://www.html5canvastutorials.com/tutorials/html5-canvas-rectangles/, I have drawn some rectangles side-by-side on a canvas. The problem is that they appear greatly zoomed in; at a zoom of 1.0 they appear approximately five times their original size; they appear correctly sized (if fuzzy around the borders) at a zoom of around 0.16.
I expect I could get a workaround by making the pixel dimensions of the canvas much greater and zooming out, but what is the proper way to get a 1:1 scaling on a canvas? The canvas is styled to width and height of 100%, and the body has a margin of 0. Manually setting the canvas's width and height to the height and width of the window does not alter this behavior.
TIA,
the problem is, you set the width and height of the style for the canvas. You need to set the width and height attributes, not the css style. so something like:
<canvas id='mycanvas' width='800' height='600'></canvas>
More info in a similar question: Canvas is stretched when using CSS but normal with "width" / "height" properties
Having trouble scaling with . It seems to make sense to code up a drawing in canvas to a fixed size (ie 800x600) then scale it for specific locations - but sizing occurs in 4 places: 1) in the context definition (ie ctx.width = 800 2) with ctx.scale; 3) in html with
I can scale it with ctx.scale(0.25,0.25) and use but this doesn't appear right - it seems to want the scale to be proportional.
css sizing simply makes it fuzzy so not a good way to go. Any ideas?
Actually, you can resize a canvas using stylesheets. The results may vary across browsers as HTML5 is still in the process of being finalized.
There is no width or height property for a drawing context, only for canvas. A context's scale is used to resize the unit step size in x or y dimensions and it doesn't have to be proportional. For example,
context.scale(5, 1);
changes the x unit size to 5, and y's to 1. If we draw a 30x30 square now, it will actually come out to be 150x30 as x has been scaled 5 times while y remains the same. If you want the logo to be larger, increase the context scale before drawing your logo.
Mozilla has a good tutorial on scaling and transformations in general.
Edit: In response to your comment, the logo's size and canvas dimensions will determine what should be the scaling factor for enlarging the image. If the logo is 100x100 px in size and the canvas is 800x600, then you are limited by canvas height (600) as its smaller. So the maximum scaling that you can do without clipping part of the logo outside canvas will be 600/100 = 6
context.scale(6, 6)
These numbers will vary and you can do your own calculations to find the optimal size.
You could convert the logo to svg and let the browser do the scaling for you, with or without adding css mediaqueries.
Check out Andreas Bovens' presentation and examples.
You can resize the image when you draw it
imageobject=new Image();
imageobject.src="imagefile";
imageobject.onload=function(){
context.drawImage(imageobject,0,0,imageobject.width,imageobject.height,0,0,800,600);
}
The last 2 arguments are the width an height to resize the image
http://www.w3.org/TR/html5/the-canvas-element.html#dom-context-2d-drawimage
If you set the element.style.width and element.style.height attributes (assuming element is a canvas element) you are stretching the contents of the canvas. If you set the element.width and element.height you are resizing the canvas itself not the content. The ctx.scale is for dynamic resizing whenever you drawing something with javascript and gives you the same stretching effect as element.style.
I have a mask i'm using for a continuous scroll type thingy, and notice that when my masked sprite gets past a certain pixel size in height (2878) the mask does not mask. Has anyone experienced this? is this a bug?
to reproduce:
create a sprite over 2878 px in height and apply mask, mask breaks
create a sprite 2877 px in height and apply mask, mask works
I can't verify if that is a hard limit, but there are a bunch of similar size limits for bitmaps in Flash that crop up in various areas. One potential solution would be to use the scrollRect property of your content display object. When you set scrollRect you are essentially creating a rectangular mask and I'm almost positive I've done it with 5000+ pixel wide sprites in the past.