I've been searching for answer for about 2 hours now and I haven't found my desired answer. My question is, Is it possible, and how, to draw a circle-shaped texture, so that outside the circle, texture would be transparent, is it even possible?
Thanks in advance! This site has been a great help so far!
The easiest way is to open a program like Photoshop and make an image with an alpha-channel. That means: Start with a completely transparent image and draw a circle on it. Then save it as .png
You can then just load it in your game and render it using a SpriteBatch. It (or better your graphics card) knows how to handle the alphachannel and will keep everything but the circle completely invisible.
This way you do not have to manipulate any pixmaps at runtime and you are not limited to simple shapes like circles.
If the portion of the texture you want to see in the circle is not meant to change during execution, the easiest way is to open Photoshop, make what you want, export it as an image and then load it in a Texture or a Sprite object in your code.
But this can also be done at runtime, via OpenGL using a Stencil test. This is the only solution if the portion displayed in the circle will have to be alterable during execution.
pixmap use this link if u are using other than .png format for your images
Apart form it if you are using png images then just draw the cirlce. Outside the circle will remain transparent.
Related
I am trying to make an 'Eraser' for my fabricjs-based 0.5 Opacity free drawing app(with non-trivial background image), i. e. everything drawing is half-transparent and we still can see the background through the free drawing.
However I understand by default all free drawing are 'path-based' i. e. everything we draw (between mouse-down mouse up) is captured as an individual path in the canvas, so it is not possible to erase arbitrary part of the path. So I am thinking maybe we can capture the mouse-down/up event manually and draw an image pixie by pixie and place it on the canvas with opacity=0.5? so that we can use white to overwrite all those 'old' drawing?
Is this a workable/efficient enough solution?
However I am not sure how this can be implemented in fabricjs? could you please give me some advise on the steps or some pseudocode? thanks
I didn't complete my attempt when i had a similar problem , but the basic concept was simple 'Read the pixel under the cursor(and under the canvas, where another canvas with a background image was) and paint the path with the same color' , creating an eraser effect. The starting stone was this jsfiddle.net/DV9Bw/1/ maybe it can help you out, i didn't try it to its completion since the idea was quickly abandoned
I was wondering how one would go about automatically making an image map based on just the opaque parts of a png image. You are normally able to click anywhere on the png image, even transparent areas, and it will register as clicking the image. Is there any way to exclude transparent areas and only have opaque areas register?
I assume there is some sort of javascript color detection feature, or something along those lines. I have access to jQuery on my website, as well.
Thank you for taking time to read and answer.
Trying to do this with images will be a major headache. It's possible that there is a javascript library out there to detect colors, but that's very complex stuff.
Maybe give svg a go if the graphics are simple.
This site (not mine) has a nice map using svg.
In my web application I want the user to be able to draw some rectangles on an image, also change the size of the rectangles and drag and drop them. after that I have to get coordinates of rectangles and send them to server's database
Is it better to create a canvas on a photo or load the image in canvas ?
I don't write any code yet because I have no idea how to do this.
Any ideas,suggestions,links,libraries ?
As the comment said canvas is a good bet for this, but you'd need to do a fair bit of coding to get it working.
I actually have a tutorial on making Canvas interactive by drawing rectangles and moving them around. It should give you a good start on this project.
There are also a few libraries, such as fabricJS, but that might be hard to get the coordinates out of without digging into the library.
I noticed that many of the sprites on the internet has a solid color background and not transparent i am sure there is a reason behind that but what is it ?
like this one :
http://www.spriters-resource.com/gameboy_advance/gs2/sheet/47045
I can remove the bg using photoshop but if this was the purpose why people didn't save it as transparent png in the first place.
what is the easier way to use this sprites in flash it doesn't make sense to me to cut each one and put it in a separate frame i am sure there is an easier way.
Sprite sheets are not meant to be sliced up into different images before compilation. Rather, they are mainly used for a technique called blitting which involves copying the pixels from the spritesheet onto the display at runtime (traditionally done for a performance gain over the standard Flash display list rendering).
You can read up on blitting here: http://www.8bitrocket.com/2008/7/2/Tutorial-AS3-The-basics-of-tile-sheet-animation-or-blitting/
And on how to actually remove the background when blitting: http://active.tutsplus.com/tutorials/animation/blitting-with-as3-removing-a-bitmaps-background-color/
I have a basic paint application on a canvas, and I want to make a drawing-border and by that create a stencil. In other words, I want to make a shape, and then I want the user to be able to draw only inside it, even when he tries to draw outside.
Do you have any idea how can i do it?
thanks
This can be achieved by making a clipping region. The basic idea is that there is a path on the canvas that all drawing is constrained to.
Make the shape, and instead of calling stroke() or fill(), call clip()
If you don't quite get how clipping regions work, there are a few examples around.