Pixel precise touches / touches through alpha channels

Dro

Hello guys. I'm new with objective-c and Sparrow, so maybe my question will look stupid.

For now I have several 'SPSprites' with 'png' images inside. My problem is that Sparrow handles touches for entire image box, not just used area of it.

Here I made an example http://pix.academ.org/img/2012/02/26/3a27e7d72fff2c4cc3c68884ec428b08.png

You see, blue and green sprites cover orange and pink ones, so it will interfere the touches.

I want to implement pixel precise touches for that project. Hope there was some option on touch event to use or not to use this behavior as default.

Or at least if I could determine a touch of an alpha channel or 'useful' data of an image that would help.

It also would be nice to check clicks not only on 'imageWithContentsOfFile' but also on SPSprite containing that image considering rule described higher.

Thank you for any help.

nilaf_prince

I am not sure whether i completely understand your problem.

You want to receive touch events for the object hidden behind blue and green images .

http://forum.sparrow-framework.org/topic/touch-area#post-8513

Dro

not hidden behind images itself. I mean 'useful area' of it

I redrew the image for better understanding

http://pix.academ.org/img/2012/02/26/5ef7200011d57493745d3b5176cba119.png

so red zones 1 and 2 suppose to belong to Yellow area.
3 for Green
4 and 5 for Pink

right now 1 and 4 belong to Green
2,3,5 belong to Blue.

That's because of different depth of those images. Blue > Green > Pink > Yellow

Overriding hit test for every type of object is a pain. But I'm ready to do this if I know where the alpha channel on the image is. How to determine it?

So now it's clear? I should apologize for my English.

I don't believe I'm the first one who's asking for help with this problem.

nilaf_prince

I have not tested . There is a post about the same in detail.Source code also shared. That should help.

http://forum.sparrow-framework.org/topic/touches-in-opaque-area-of-png#post-11247

Daniel

Exactly -- the "hitTest" method is the way to go. Good luck!
BTW, welcome to the Sparrow forum! =)

Dro

Yeah. I made it. and it was fun )

But it would be better to have internal flag for ignoring alpha channels in touch event.

Maybe in sparrow 2.0? 😉

Daniel

The problem is that I can't access the individual pixel data once it is a texture object; so I'd have to keep a reference to the bitmap data, which would take up a lot of memory. However, I know that it's a common thing to do, so I'll think about other ways to make that more simple! =)

Dro

Looks like it has been broken in Sparrow 1.3

hitTestPoint works realy strange. Some areas of SPDisplayObject do not test hit points.
Maybe it sounds not so truthfully but I got the same behavior in SP1.2. But it was all good in last git version before 1.3 update.

Can you help me please?

here's the code:

.
- (TouchableZone*)hitTestPoint:(SPPoint*)localPoint forTouch:(BOOL)isTouch
{
     NSLog([NSString stringWithFormat: @"zone %i point %ix%i data is %@ ", _zoneId, (int)localPoint.x, (int)localPoint.y, [self isDataInPoint:localPoint] ? @"YES": @"NO"]);
    if(![GameSettings getAllowControls]) return nil;

    if ([self isDataInPoint:localPoint]) return self;
    else return nil;
}

Sometimes even NSLog won't appear at all.

Shilo

@Dro

Looks like I created an extension for this purpose awhile back, I just now found it, updated it, and tossed it on the wiki.

If you are curious about the old post, you can find it here: http://forum.sparrow-framework.org/topic/irregular-button#post-8719
And you can find the wiki for it here: http://wiki.sparrow-framework.org/extensions/shalphatexture

Give me a shout out if you decide to use it and need help.

Regarding your question above: I don't see what would cause the hitTestPoint:forTouch: not to be called, unless the sparrow view/stage isn't receiving the touch, which would mean there is a UIKit element blocking it.

Dro

hmm. for some strange reason with my pictures it works the same way as it was before

the new code is

- (TouchableZone*)hitTestPoint:(SPPoint*)localPoint forTouch:(BOOL)isTouch
{
    if(![GameSettings getAllowControls]) return nil;

    if([spImage alphaOfPixelWithX:localPoint.x y:localPoint.y]>0){
        return self;
    } else return nil;
}

spImage is SHAlphaImage now

even trace in here doesnt work in some cases. even if I click on image area.
so maybe the problem of migrating to 1.3 is only with hitTestPoint itself.

Shilo

SHAlphaImage already does the alpha handling in its hitTestPoint:forTouch: method. All you need to do is change "allowTouchOnAlpha" property to whatever value that suits you. If you share your project or a sample project of the issue, I will have a look.

Dro

if I set my zone to touchable = YES and remove hitTestPoint inside of it
I see

2012-03-14 03:53:42.006 sf[21352:10a03] -[SHAlphaImage getId]: unrecognized selector sent to instance 0x8981eb0
2012-03-14 03:53:42.007 sf[21352:10a03] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[SHAlphaImage getId]: unrecognized selector sent to instance 0x8981eb0'
*** First throw call stack:
(0x1cc7052 0x19c6d0a 0x1cc8ced 0x1c2df00 0x1c2dce2 0x9357 0x1c2d51d 0x1c2d437 0x23944 0x1660b 0x23b3d 0x1660b 0x23b3d 0x1660b 0x11a02 0x198f4 0x266c4 0x25f82 0x41d93f 0x41dc56 0x404384 0x3f7aa9 0x22b4fa9 0x1c9b1c5 0x1c00022 0x1bfe90a 0x1bfddb4 0x1bfdccb 0x22b3879 0x22b393e 0x3f5a9b 0x1e29 0x1d75)
terminate called throwing an exception(gdb) `

if touchable == NO (or YES, doesn't matter), but there is hitTestPoint inside. it works partly. I can't find the correct logic to explain how it determines touches.

is it possible that the reason of this in png files themselves?
I can upload it somewhere.

here we are https://dl-web.dropbox.com/get/zones.zip?w=4edbf57f

and the project itself. https://dl-web.dropbox.com/get/sf%20wtf.zip?w=93f54b5a
We're talking about TouchableZone class. Zones are being set in ZonesController.

sorry. it's my first meeting with obj-c and sparrow. so don't blame me for dirty code.

Shilo

When I try to download the files from the links you provided, I get:
"Error (403)
It seems you don't belong here! You should probably sign in. Check out our Help Center and forums for help, or head back to home."

I have even signed in and still get the same error.

I suggest you get cloud app and upload it to that server.

Dro

I'm so sorry about that
http://www.mediafire.com/download.php?b4ga4n4bfazu08p
http://www.mediafire.com/download.php?bi4y2jvif46vvb4

I will try to put all touch handlers inside TouchableZone instead of ZonesController.
but I don't see the logic.

looks like touch.target gives me SHAlphaImage inside of TouchableZone. instead of TouchableZone itself.

update, this had not effect. I'm starting to blame pictures again. Will try different.

Shilo

I was able to get the touch working correctly, although, due to your code structure, I wasn't able to do it the way I intended it. Here are the steps you need to take...

In ZonesController.m:

Replace addTouchEvent: method with...

-(void)addTouchEvent {
    [[SPStage mainStage] addEventListener:@selector(onTouchEvent:) atObject:self forType:SP_EVENT_TYPE_TOUCH];
}

Replace removeTouchEvent method with...

-(void)removeTouchEvent {
    [[SPStage mainStage] removeEventListener:@selector(onTouchEvent:) atObject:self forType:SP_EVENT_TYPE_TOUCH];
}

Replace onTouchEvent: method with...

- (void)onTouchEvent:(SPTouchEvent*)event
{
    //if(![GameSettings getAllowControls]) return nil;

    NSArray *touchesBegin = [[event touchesWithTarget:[SPStage mainStage] andPhase:SPTouchPhaseBegan] allObjects];
    NSArray *touchesEnd = [[event touchesWithTarget:[SPStage mainStage] andPhase:SPTouchPhaseEnded] allObjects];

    if(touchesBegin.count){
        for(int i=0; i<touchesBegin.count; i++){
            SPTouch *touch = [touchesBegin objectAtIndex:i];
            for (TouchableZone *touchableZone in zonesArray) {
                SHAlphaImage *image = touchableZone.spImage;
                SPPoint *location = [touch locationInSpace:image];
                if ([image alphaOfPixelWithX:location.x y:location.y] >= image.allowTouchOnAlpha) {
                    lastPressedZoneIndex = [touchableZone getId];
                    [touchableZone click];
                    break;
                }
            }
        }
    }

    if(touchesEnd.count){
        for(int i=0; i<touchesEnd.count; i++){
            SPTouch *touch = [touchesEnd objectAtIndex:i];
            for (TouchableZone *touchableZone in zonesArray) {
                SHAlphaImage *image = touchableZone.spImage;
                SPPoint *location = [touch locationInSpace:image];
                if ([image alphaOfPixelWithX:location.x y:location.y] >= image.allowTouchOnAlpha) {
                    lastPressedZoneIndex = [touchableZone getId];
                    [touchableZone unclick];
                    break;
                }
            }
        }
    }
}

In TouchableZones.h:

Add this property...

@property (nonatomic, readonly) SHAlphaImage *spImage;

In TouchableZones.m:

Add this synthesize...

@synthesize spImage;

... and that should do it. The key problems you had were: First, the touches weren't always caught by the zone controller sprite, so you have to handle to touches on the stage instead. And second, the target of the touches weren't always TouchableZone, so instead you should just loop each TouchableZone to make sure the touch is within them.

BTW, I love the background animations. It's very pretty and entertaining.

Dro

Thank you very much Shilo. That works; Even if I got new problems I will handle it.

This was little bit uncommon for me as flash developer. Now I got the point. but there are still a lot of things I have to learn.

Dro

Hi Shilo.
I'm sorry to ask you. But is it possible to update your SHAlphaImage for Sparrow2.0?

there's no SPTextureFormat, no SPColorSpaceRGBA and etc.

That's funny how 1 year later I have mostly the same task with pixel precise touches as before.
I got this. you can check texture alpha only on UIImage. and not SPImage or SPTexture. There's also no way to init UIImage with SPTexture.

Guys, I need one quick tip.

Shilo

Updated the extension to ARC and Sparrow 2.0.

You can find the new source code here:
https://gist.github.com/Shilo/6577834

And the new sample project here:
http://cl.ly/RPR4

I didn't have time to test everything, but the sample project works.

Dro

Thank you for quick response.

I suppose I can use it like that:

init SHAlphaImage with SPTexture [SHAlphaImage imageWithTexture:_texture]
put it inside of SPSprite.
and in this sprite hittest:

if([self.shAlphaImage alphaOfPixelWithX:localPoint.x y:localPoint.y]) {
        NSLog(@"\n\n\nBINGO\n\n\n");
        return self;
    }

otherwise return just nil;

for now I can't make it work because in SHAlphaImage:

- (float)alphaOfPixelWithX:(float)x y:(float)y {

    SHAlphaTexture *texture = (SHAlphaTexture *)self.texture;
        NSLog(@"%i,%i,%i",[texture isMemberOfClass:[SHAlphaTexture class]],[texture isMemberOfClass:[SHAlphaSubTexture class]],[texture isMemberOfClass:[SHGLAlphaTexture class]]);

gives me 0,0,0

so SHAlphaImage contains just a usual SPtexture. and not SHAlphaTexture. I guess.

textures are from atlas. So I can't init new SHAlphaTexture with name. Probably it's possible with atlas texture and small region. But I would love to see straight forward SPTexture -> SHAlphaTexture conversion. Please point me.

Shilo

You are correct, the texture needs to be SHAlphaTexture to get the alphaData from the texture. The only real difference between SHAlphaTexture and SPTexture is that, SHAlphaTexture is forced to be loaded as a UIImage and then the alpha data from the UIImage is cached. So there would be no way to convert an SPTexture to SHAlphaTexture.

The only way to get the alpha pixel data from sub textures of a texture atlas, is to load an atlas texture with UIImage and get the alpha data for the whole atlas texture. This might not be the best approach because caching the alpha data of a whole texture atlas probably wouldn't be optimal and could also use a considerable amount of virtual memory. Not only that, I would need to create a new SHAlphaTextureAtlas class to handle this, which I don't have the time for that.