In the case where an image is overlaid on top of a different image, I would like to have vision of the background image while cropping the foreground image at same time.
Example: Image A is on top of Image B. Jcrop is applied to Image A and when a selection occurs, the area of selection shows only the selected part of Image A. Image B is visible in the background, surrounding the area of selection of Image A.
Is this possible?
$(function($){
$('#target').Jcrop({
bgColor: '',
bgOpacity: 0
});
});
Related
If you click Run code snippet in this link, it shows a cool usage of <canvas> where you can "cut-out" part of the image (just drag your mouse on the image to "cut"). I'm just curious if there is any way to save the resulting "cut-out" part of the image, as a transparent PNG (i.e. everything that is white in the canvas would be transparent).
If anyone can point me in the right direction (or tell me it's not doable), I'd appreciate it.
Yes, there is a way. Use canvas context.getImageData to get image raw data-array. Do with it(raw data) what you need(make transparent any pixel you need), and then use context.putImageData to render data on canvas. Then use var data = canvas.toDataURL("image/png") to get image data. And then you can do so: image.src = data;
Use this link https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/getImageData for more info
Here's a quick tour showing how to crop & save a user-dragged cutout of an image:
Draw the image on the canvas.
Listen to mouse events and let the user define the region they want to cut out by continuously connecting new lines to the current mouse position.
Save every mouse point from #2 in an array.
When the user has finished defining their cutout region:
Clear the canvas.
Draw and fill the cutout area using the saved points in the arry.
Set context.globalCompositeOperation='source-in'. This mode will cause any new drawings to appear only where the newly drawn pixels and the existing pixels overlap and every thing else is made transparent. In common terms: New pixels will be "clipped" into the user defined cutout and new pixels will not appear outside the cutout.
Redraw the image.
The result is the second drawing of the image will appear only inside the user defined cutout. Everything else will be transparent.
Finally, you can use var url=canvasElement.toDataURL to save the cropped canvas image into a .png dataURL. If you then want an actual image from this dataURL you can var img=new Image() and set the img.src=url.
I'm working on a project that has some draggable content in it. All of the images that are draggable have portion that are transparent and overlap other content.
I set up an example on JSFiddle: Draggable Example
<body>
<p>The background is transparent, but if you grab ANYWHERE in the border you can drag the image around.</p>
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Jupiter_(transparent).png/484px-Jupiter_(transparent).png"></img>
</body>
img{
border: solid black 1px;
}
In the example you can grab the image by holding down the left mouse button anywhere within the borders of the image, even if they are transparent. In this example my goal would be to only be able to drag the image if you grabbed a visible portion of the planet Jupiter.
Is this possible in html?
Based on your clarification in comments above, it might be easiest to draw the images in a canvas element. You can add draggability to the canvas as explained in this SO post: Make image drawn on canvas draggable with JavaScript. And you can modify that to trigger the drag flag only if a non-transparent pixel is at the clicked position.
I'd like to know if there is some way in Kinetic to have an image merged with another image on a lower layer, creating a kind of crop effect based on the shape of the "cropping" image.
The image must have a transparent background as a result, which is the main source of difficulty for me. I would otherwise just have used a mask with dragging turned off... I've made a diagram to explain what I want a bit better. Any suggestions welcome.
diagram
I've also made a quick jsfiddle, where I would like the contents of the image to be displayed inside the box. I feel like one layer is the way to go on this one.
You can use an offscreen Canvas element plus compositing to create your clipped image for use by your Kinetic.Image. Note that the offscreen canvas can be used as an image source for your Kinetic.Image.
Example code and a Demo: http://jsfiddle.net/m1erickson/ks1xxqfL/
var canvas=document.createElement('canvas');
var ctx=canvas.getContext('2d');
canvas.width=background.width;
canvas.height=background.height;
ctx.drawImage(mask,0,0,mask.width*2.25,mask.height*2.25);
ctx.globalCompositeOperation='source-in';
ctx.drawImage(background,0,0);
var support=new Kinetic.Image({
draggable:true,
image:canvas,
});
layer.add(support);
layer.draw();
Illustrations
Left: the background image,
Center: the image to be used as a clipping mask
Right: the background clipped by the mask (mask was scaled by 2.25X)
My canvas has a background image. That image has different part such as level-1,level-2 etc. I will create few buttons. When button-1 is clicked only show level-1 portion of background image and hide other levels. Similarly for button-2 is clicked only show level-2. For example the background could look like this image:
I have a canvas <canvas></canvas> that displays a graphic of an unclean window. I need to be able to 'clean' the window with my cursor, displaying another image behind it. Just as this website uses their brushes: http://mudcu.be/sketchpad/ but rather than adding to the page, I need to remove content to display the image behind it.
Here's an example of the before and after 'rubbing out':
http://www.titaniumwebdesigns.com/images/forums/before.png http://www.titaniumwebdesigns.com/images/forums/after.png
See this complete DEMO
globalCompositeOperation is one of the most nice features in canvas api.
To achieve the desired effect, I use multiple canvas layers and globalCompositeOperation.
In this solution we have 3 layers:
Layer 1 - bottom Layer 2 - middle
Layer 3 - top
Middle and Top layers are static and only the middle layer is dynamically cleared using globalCompositeOperation.
middleCtx.globalCompositeOperation = "xor";
With globalCompositeOperation = "xor", the brush is drawn over the layer and clears the portion of canvas where it was drawn.
The final result is:
UPDATE:
To verify if the window is fully cleaned I create a hidden canvas with the same size of the others layers and drawn a black rectangle on it. When dragging the mouse over the canvas the layer 2 (middle) is cleared with a circle with transparent gradient color and now we also draw over the hidden canvas a circle with white color (might be any color different of black).
So on, we just verify the pixels of the hidden canvas and if there is no black pixels, the window is cleaned.
To get the image data we need to use something like:
imageData = context.getImageData(x, y, width, height)
and then get the pixels from the image data:
pixels = imageData.data;
The requestAnimationFrame routine is used for performance reason, because getImageData might be slow. The major change in the code is put the brush action inside an animation frame when dragging the mouse instead of do that action in each mouse move event. This allows the processor to have more time to do the pixel data verification.
Here is the modified fiddle with pixel data verification and an alert when the window is cleaned:
jsFiddle link
If you have a canvas where you have drawn a blurred image into it once, you should be able to create that effect by creating a "brush" image (an image containing a semi-transparent circle, with soft edges), and then draw that image in the canvas at the mouse coordinate using:
canvasContext.globalCompositeOperation = "destination-out";
https://developer.mozilla.org/samples/canvas-tutorial/6_1_canvas_composite.html
As soon as you have drawn the blurred image to the canvas, you just need to call the line above once and all drawn images after will use the specified composite operation.