I'm trying to give ccsprite blink effect by adjusting brightness.
so I need to adjust contrast of ccsprite.
How to do that?
CCSprite* ccs_sprite = CCSprite::create("button.png");
ccs_sprite->setPosition(ccp(500, 500));
ccs_sprite->setContrast()???
addChild(ccs_sprite);
You can get a blink effect by adjusting the opacity of the sprite with the setOpacity method and alternatively using the CCFadeIn, CCFadeOut and CCFadeTo actions.
Edit:
There is also the CCTintTo and CCTintBy actions that will adjust the RGB colors of the node.
You can visit here for detail reference about classes in cocos2d-x
http://www.cocos2d-x.org/reference/native-cpp/V2.2/d4/de7/classcocos2d_1_1_c_c_sprite.html
Related
My goal is to bring in an image on to part of the canvas, then scale it, move/translate it, and optionally skew it, also rotate and make alpha changes, kind of the primary "2d image manipulations", in an animated form, which is: do little changes over time from the starting state to the target end state.
Well, I figured to be efficient, I should use the canvas/2d context transform, https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/transform -- as it does the first 3: scale, move/translate, and skew, "all in one." I did half that code, and now I'm looking at examples and seeking to debug it. All the examples I see, are do 1) some transform, away from the "unity transform":
{ a:1, b:0, c: 0, d:1, e:0, f:0 }; // this basic transform does nothing
and then 2) draw into that. But that's the opposite order from what I want: which is draw on the canvas (the image), and then do an animation over time using the above primary changes (scale, translate, skew, rotate, and alpha). My question is: does it only "work this way", meaning I must setup the (single) transformation on the page first, and then "draw into that?"
I hope not ... that won't give me what I want, and I have to "ditch it", and go to 5 individual "transformations." Comments?
Yes that only works this way, canvas transforms and compositing mode and filters and lineWidth and fillStyle etc. properties are only applied to the next drawing operations.
The canvas itself only holds pixels information, it has no concept of drawn object. Your js code has to do this part.
So for what you wish, you can simply redraw everything every time:
reset the transform so we can clear ctx.setTransform(1,0,0,1,0,0);
Clear the canvas ctx.clearRect(0,0,ctx.canvas.width,ctx.canvas.height)
Set the transform to your new matrix ctx.translate(x,y); ctx.scale(s)...
Draw your transformed graphics ctx.fill(); ctx.drawImage(...
Wait next frame to do it again requestAnimationFrame(update)
So I have particle effect(with additive: false) and now I want to create beautiful fade out effect. I've tried to make something like that:
Color color = batch.getColor();
batch.setColor(color.r, color.g, color.b, color.a * alpha);
but it doesn't work for particle effect.
Does anyone know how to change alpha of particle effect?
Solution was pretty simple :D
All You need is:
m_particleEffect.getEmitters().get(0).getTransparency().setHigh(0.5f/*alpha*/);
Hope this will help someone :)
If you look at the ParticleEmitter.draw code, you'll see the blend mode of the drawing is controlled by the setAdditive (which you say you have set to false) and setPremultipliedAlpha methods. It looks like you want to use pre-multiplied alpha, but I'm unsure of how the batch color interacts with the texture color in LibGDX. Try setting pre-multiplied alpha to true first.
The problem
I'm trying to create a brush tool with opacity jitter (like in Photoshop). The specific problem is:
Draw a stroke on an HTML canvas with different levels of opacity. Pixels with higher opacity should replace pixels with lower opacity; otherwise, pixels are left unchanged.
Transparency should not be lost in the process. The stroke is drawn on a separate canvas and merged with a background canvas afterwards.
The result should look like this. All code and the corresponding output can be found here (JSFiddle).
Because you can't stroke a single path with different levels of opacity (please correct me if I'm wrong) my code creates a path for each segment with different opacity.
Non-solution 1, Using the 'darken' blend mode
The darken blend mode yields the desired result when using opaque pixels but doesn't seem to work with transparency. Loosing transparency is a dealbreaker.
With opaque pixels:
With transparent pixels:
Non-solution 2, Using the 'destination-out' compositing operator
Before drawing a new stroke segment, subtract its opacity from subjacent pixels by using the 'destination-out' compositing operator. Then add the new stroke segment with 'source-over'. This works almost but it's a little bit off.
Looking for a solution
I want to avoid manipulating each pixel by hand (which I have done in the past). Am I missing something obvious? Is there a simple solution to this problem?
"Links to jsfiddle.net must be accompanied by code."
Because you can't stroke a single path with different levels of opacity (please correct me if I'm wrong)
You're wrong =)
When you use globalCompositeOperation = 'destination-out' (which you are in lineDestinationOut) you need to set the strokeStyle opacity to 1 to remove everything.
However, simply changing that in your fiddle doesn't have the required effect due to the order of your path build. Build the 10% transparent one first, the whole length, then delete and draw the two 40% transparent bits.
Here's a jsfiddle of the code below
var canvas = document.getElementById('canvas');
var cx = canvas.getContext('2d');
cx.lineCap = 'round';
cx.lineJoin = 'round';
cx.lineWidth = 40;
// Create the first line, 10% transparency, the whole length of the shape.
cx.strokeStyle = 'rgba(0,0,255,0.1)';
cx.beginPath();
cx.moveTo(20,20);
cx.lineTo(260,20);
cx.lineTo(220,60);
cx.stroke();
cx.closePath();
// Create the first part of the second line, first by clearing the first
// line, then 40% transparency.
cx.strokeStyle = 'black';
cx.globalCompositeOperation = 'destination-out';
cx.beginPath();
cx.moveTo(20,20);
cx.lineTo(100,20);
cx.stroke();
cx.strokeStyle = 'rgba(0,0,255,0.4)';
cx.globalCompositeOperation = 'source-over';
cx.stroke();
cx.closePath();
// Create the second part of the second line, same as above.
cx.strokeStyle = 'black';
cx.globalCompositeOperation = 'destination-out';
cx.beginPath();
cx.moveTo(180,20);
cx.lineTo(260,20);
cx.stroke();
cx.strokeStyle = 'rgba(0,0,255,0.4)';
cx.globalCompositeOperation = 'source-over';
cx.stroke();
cx.closePath();
Use two layers to draw to:
First calculate the top layer opacity 40% - 10% and set this as alpha on top layer
Set bottom layer to 10%
Set top layer with dashed lines (lineDash) (calculate the dash-pattern size based on size requirements)
Draw lines to both layers and the bottom layer will be a single long line, the top layer will draw a dashed line on top when stroked.
Copy both layers to main canvas when done.
#HenryBlyth's answer is probably the best you're going to get; there's no native API to do what you're being asked to do (which, in my opinion, is kinda weird anyways... opacity isn't really supposed to replace pixels).
To spell out the solution in one paragraph: Split up your "stroke" into individual paths with different opacities. Draw the lowest opacity paths as normal. Then, draw the higher opacities with "desitination-out" to remove the low-opacity paths that overlap. Then, draw the high opacity paths as usual, with "source-over", to create the effect desired.
As suggested in the comments to that answer, #markE's comment about making each path an object that is pre-sorted before drawing is a great suggestion. Since you want to perform manual drawing logic that the native API can't do, turning each path into an object and dealing with them that way will be far easier than manually manipulating each pixel (though that solution would work, it could also drive you mad.)
You mention that each stroke is being done on another canvas, which is great, because you can record the mouseevents that fire as that line is being drawn, create an object to represent that path, and then use that object and others in your "merged" canvas without having to worry about pixel manipulation or anything else. I highly recommend switching to an object-oriented approach like #markE suggested, if possible.
Is it possible to only trigger a div's mouseover when the cursor is over an opaque part of the div's background image? Perhaps via Javascript?
All I can find with Google are old IE PNG fixes.
This looks like a similar question to this one: Hit detection on non-transparent pixel
I suppose this could also be done for background image by getting the attribute with jQuery:
$('#myDiv').css('background-image');
I haven't personally done this, but it seems like a viable solution. This will only work for modern browsers, but you should be able to make it back-compatible with excanvas.
It is possible, just not very easily. You'll have to use a lot of Javascript.
You'd want to attach to your <div>'s onmousemove event, which returns the X,Y coordinates of the cursor. Your event handler function would then test to see if the cursor is in the correct place in order to trigger an alternative onmouseover event.
Implementing the "is the cursor over an opaque pixel or not?" test can be done two ways: the first is to create a simple mathematical expression (say if the opaque parts of the image make neat rectangles, circles or polygons). The more difficult (and less browser-supported) way is to load the background image into a Canvas object and then get the current pixel value's opacity figure and take it from there, like so:
var pixel = canvas.getImageData(x, y, 1, 1).data;
var alpha = pixel[3]; // assuming RGBA
if( alpha > threshold ) onMouseOver(); // raise the event
Another alternative is to create an entirely transparent div (or some other element) positioned and sized so that it only covers the opaque part of the div below, then just test the mouseover of that element's box.
It's a bit of tweaking but why don't you add a class to your opaque div, and use JavaScript to check for it?
In jQuery:
$('div').mouseover(function(){
if ($(this).is('.opaque')) {
//Some actions
}
});
Here I have an arc with some transparency applied to one of the two gradients its using:`
ctx.arc(mouseX,mouseY,radius,0, 2*Math.PI,false);
var grd=ctx.createRadialGradient(mouseX,mouseY,0,mouseX,mouseY,brushSize);
grd.addColorStop(1,"transparent");
grd.addColorStop(0.1,"#1f0000");
ctx.fillStyle=grd;
ctx.fill();
Is there a way to now give the entire arc some transparency affecting only the arc and none of the rest of the canvas?
Thanks
Unlike SVG or HTML, there is no layering or grouping on an HTML Canvas. You can't wrap your arc/gradient in another lower-opacity element; you must propagate opacity (or tinting, or whatever) changes down to the end properties directly.
Your color #1f0000 is equivalent to rgb(31,0,0); use rgba to lower the opacity of this particular color stop.
var opacity = 0.55; //55% visible
grd.addColorStop(1,'transparent');
grd.addColorStop(0.1,'rgba(31,0,0,'+opacity+')');
You could make the color stop at the end an rgba color and give it transparency that way.