I'm using Phonegap to allow a user to select a photo from their library, and then edit it.
When I retrieve the photo using Phonegap, I store the image in an html img element that is already on my page:
sourceImage = document.getElementById('smallImage');
sourceImage.style.display = 'block';
sourceImage.src = "data:image/jpeg;base64," + imageData;
Of course, when the photo loads in, it could be larger than the phone screen, so I shrink it down in my img element. I modify the actual img element width and height, not the css properties, and the image is properly displaying on screen (around 288 x 200, rather than the original 1024 x 768). So, my img element is now displaying a picture (as a preview) and when the user advances to the next screen, the image is drawn on a canvas so it can be modified:
sourceImage.onload = function(){
myCanvas.drawImage(sourceImage, 0, 0);
}
The image draws correctly, however, it draws the original 1024 x 768 image retrieved from the library and not the modified, smaller image in the actual img element I am displaying on the page. I'm assuming this is due to the fact that the actual image.src is referencing an image that is 1024 x 768, even though I shrink it down.
I have not found any support for re-sizing images before storing them in phonegap. Does anyone know of way I could modify this image src size so that when I am able to shrink it before drawing it to a canvas? (Please keep in mind the user is loading in pictures on-the-fly from their library. I'd prefer to have a client-side solution, but I've not been able to find one).
when you draw the image on canvas you can specify the destination coords on the canvas an the part of the image your like to draw like this:
context.drawImage(image, source_x1, source_y1, source_x2, source_y2, dest_x1, dest_y1, dest_x2, dest_y2);
So you can draw the image in any size you like...
Related
So I just created a blog on Blogspot. And I'm currently using a simple free blog template from the internet.
You can refer my blog here - https://hariinisayarasa.blogspot.com
Im using the free template from here - https://www.way2themes.com/2020/08/sylva-blogger-template.html
As you can see, you can compare the slider image on my blog is blurry and pixelated compared to the one on the Demo Page here - https://sylva-way2themes.blogspot.com/
Is there any way I can resize my image or any setting that can be done in my template coding so that the slider images are not blurry anymore?
Please let me know if I can provide any code for you so that you can help me solve this problem.
Or you can download the code here - https://www.way2themes.com/2020/08/sylva-blogger-template.html
One of the simplest ways to resize an image in the HTML is using the height and width attributes on the img tag. These values specify the height and width of the image element.
Resizing img with HTML
<img src="https://ik.imagekit.io/ikmedia/women-dress-2.jpg"
width="400"
height="500" />
Resizing img with CSS
img { width: 400px, height: 300px}
From what I've seen, you're using very small raster images.
notice the 'intrinsic size' property
same goes here
Photographs are always saved as raster images. It means that the data of an image is stored in the form of a pixel map - a matrix of squares. If you try to scale the image up, every pixel is also scaled up. Therefore, you lose quality, and the pictures seem pixelated/blurry.
There's no way to keep both the size and detail. Alternatively, you could try to keep the initial size of an image (or at least scale down) - this would, on the other hand, not fill the entire container space.
now check the intrinsic size of one of the images on the demo page
The more scaled image is, the more blurry it gets. The pictures on the demo page have the scale aspect of 2. However, your photo that is 72 x 72px has been scaled up a lot more.
If those photos have been taken by you in higher quality, you might want to use the raw version.
Html canvases have max sizes depending on device/browser. Eg some mobiles have roughly a 1000x1000 canvas max. What about images stored in memory? Can these be up to the ram of the phone/pc? Can you 'drawImage' large images to these 1000x1000 canvases where it does auto-cropping? (I don't have a phone to test this even for a specific device.)
The max size of an image object is probably browser or memory dependent.
More to your question...
The image object you draw into the canvas can be larger than the canvas.
This causes the canvas to become a "viewport" into the image.
For example:
Your canvas is 1000x1000.
Your image is 1500x1500.
If you do this then the image pixels will be cropped at x>1000 and y>1000.
// canvas shows image pixels from x=0-999 and y=0-999
drawImage(yourImage,0,0)
If you do this then image pixels will be cropped at x<200 & x>1200 and y<200 and y>1200.
// canvas shows image pixels from x=200-1999 and y=200-1999
drawImage(yourImage,-200,-200)
A mental exercise to see how this works is to imagine a piece of paper with a rectangle "viewport" cut from it. Then move a larger-than-viewport image behind the paper. Only a part of the image will only be visible through the viewport. You can move the image and a different portion of the image will be revealed in the viewport.
Is it possible to set the width and height of a canvas element and have the existing content scale to fit these new dimensions?
Right now the user uploads an image and my page creates a canvas element containing this image and whose dimensions are the same size as the image. I want to limit the size that I'm working with, however, so here is an example of what I want to have happen:
The user uploads an image that is 1600 x 1200 pixels (Not saved to server)
The data goes right to an html5 canvas object
The canvas height and width are set to 800 x 600 and the image content scales appropriately and then is displayed.
Right now if I set the canvas width and height it just crops the image at those dimension, not resizing as I would like. Thanks!
There are many ways to call drawImage
One is:
ctx.drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh)
Where dx,dy,dw,dh are the destination x, y, width, and height.
If you make dw and dh always 800x600, the image will drawn will always automatically be scaled to 800x600.
Here's a tiny example that will always draw any size image to 800x600 http://jsfiddle.net/jAT8Y/
Another alternative is to use context.scale function. Your image quality will remain better if you use scale.
I've just started working with the html5 canvas element.
I'm using the latest firefox and chromium browsers. And so far, they're
responding alike.
What I'm trying to achieve is scaling of an image without having to
specify the canvas or image drawing sizes. I'd like the canvas to fill
the browser window, and for the image to fill the canvas without
specifying any sizes. And to readjust canvas and its image on the
fly when the user adjusts the browser's frame.
The mansion pic that I'm testing with is 4284x2844.
I've managed to achieve dynamic scaling, but there's a problem...
if I don't specify sizes the image becomes blurry.
This is my first stackoverflow question and I haven't conquered the
formatting. So, please take a look at the small amount of code over
at pastebin:
http://pastebin.com/88faqJUx
Thank you for your help.
I found the solution...
Adding two lines, with no other changes, did the trick, though at this point I'm not exactly sure
why it was originally failing, but thoroughly happy to move on...
<canvas id="taba_main_canvas">
Your browser does not support the canvas element.
</ canvas>
<script type="text/javascript">
var main_canvas=document.getElementById("taba_main_canvas");
var cxt=main_canvas.getContext("2d");
// adding these next two lines solved the blurriness issues
//Set the canvas width to the same as the browser
main_canvas.width = window.innerWidth;
main_canvas.height = window.innerHeight;
var img=new Image();
<!-- mansion pic 4284x2844 -->
img.src="images/mansion_3344.png";
img.onload = function()
{
<!-- use the graphics full size and scale the canvas in css -->
cxt.drawImage(img,0,0,main_canvas.width,main_canvas.height);
}
</script>
Just one tiny little problem, the vertical size of the image is apparently just a few lines taller
than the canvas and so I get a vertival scrollbar. Dragging the browser window taller, which normally
would eliminate the vertical scrollbar has no effect. I've tried manipulating the canvas or image height
in the code, but that didn't change anything.
Still, having the image look clean is a big win. I'm moving on for the moment and will revisit this
later.
The other way to do this is to latch on to the document onresize event and resize the canvas by using window.innerWidth and window.innerHeight or some such thing. I've used it that way myself, but that was for something which I didn't care about IE support - see W3C DOM Compatibility - CSS Object Model View at quirksmode for info about browser support. Note also that the scrollbar width is included in innerWidth and innerHeight; if your page may need scrolling, you may wish to do something like subtract 20 and pad the containing element with a suitable background colour.
I presume that you're not just trying to draw an image - if you were just doing that, <img> would be a much better match.
Edit: jQuery has $(document).width(); and $(document).height(); which seem to get the right figures. Another edit: actually they're wrong; they're the document width and height, not viewport width and height, so I think innerWidth and innerHeight may be all there is.
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.