Pinchzoom

IQ_QI · February 2013

Hey guys
I implemented pinchzoom in my game yesterday but if I zoom my Levelsprite is always zoomed to the upper left corner.
Since there is no setAnchorpoint function available for a sprite I'm kinda stuck. Does anyone know how I zoom where the center of my zoom is in the middle of my both fingers?

Regards
IQ_QI

thanhquan1512 · February 2013

Since there is no setAnchorpoint function available for a sprite I'm kinda stuck.

Here you are:
http://www.giderosmobile.com/documentation/reference_manual.html#Bitmap:setAnchorPoint

Mells · February 2013

Source : @ar2rsawseen

Well theoretically zoom center would be the same as your anchor point. You can copy anchor point implementation

< Tell the world that this is for Sprites >
SPRITE SPRITE SPRITE SPRITE
*********************for Sprites and Sprite inherited objects*********************
SPRITE SPRITE SPRITE SPRITE
</ Tell the world >

for GiderosCodingEasy:
https://github.com/ar2rsawseen/GiderosCodingEasy/blob/master/GiderosCodingEasy.lua

twisttap · February 2013

I have a similiar problem with anchorPoint. I created a camera class with target following, parallax layers and zooming. When I try to use zoom with tween, because of the anchor point is TL corner, everything start to scaled from there and also I am kinda stuck.
@thanhquan1512 the link you provide is for Bitmap however in my state and also IQ's its related to sprite

(

OZApps · February 2013

while there is no setAnchor for other objects than Bitmaps, alignment can be managed if you use a little math which can position it accordingly.

This works fine until you start to rotate the object, which is when everything starts to go turtle.

@twisttap, try a little math and setPosition to get what you want. You can get the Width and Height of the object, you know the final x and Y positions, so now it is as simple as adding or subtracting from these x,y to get the final position.

In fact I am writing an article on this, will post the link here soon.

OZApps · February 2013

Here is the article that I was talking about

http://howto.oz-apps.com/2013/02/positioning-display-objects.html

OZApps · February 2013

@Twisttap, like the rotation, the scaling and specially when tweening, we are left helpless, however if you are using GTween, you get an event for every step of the tween, maybe you can use that event and reposition the object being tweened accordingly.

IQ_QI · February 2013

well this seems to be even more tricky then i tought cuz;
If I set the anchor point every time new if i strat pinchzooming how do i check within my camera file if the viewport bounds are reached ?? and how does it affect my touch point calculation ? ;D

 
				offsetX = event.touch.x - startx
				offsetY = event.touch.y - starty
				totaloffsetX = totaloffsetX + offsetX
				totaloffsetY = totaloffsetY + offsetY
				camera:update()
				startx = event.touch.x
				starty = event.touch.y
 
self:add_particle(math.floor(((startx - totaloffsetX)*(1/gameLayer:getScaleX()))/32)*32 +16,math.floor(((starty - totaloffsetY)*(1/gameLayer:getScaleY()))/32)*32 +16)
 
function Camera:update()
 
 
	if(totaloffsetX >= 0 ) then totaloffsetX =0 end
	if(totaloffsetX <= (0- (worldWidth + worldWidth*totalscale - self.screenWidth))) then totaloffsetX = 0- (worldWidth + worldWidth*totalscale - self.screenWidth) end
	if(totaloffsetY >= 0) then totaloffsetY = 0 end
	if(totaloffsetY <= (0-(worldHeight + worldHeight * totalscale - self.screenHeight))) then totaloffsetY = 0- (worldHeight+ worldHeight * totalscale- self.screenHeight) end
	gameLayer:setPosition(totaloffsetX,totaloffsetY)
 
 
 
 
end
 
 
function Camera:zoom(nscale)
	local new_scale =0
 
	deltascale = nscale - oldscale
 
 
	if(totalscale < -0.45) then
		if (deltascale > 0) then
			new_scale = 0.05
		end
	end
 
		if (totalscale > 2) then
			if (deltascale < 0) then
			new_scale = -0.05
			end
		end
 
	if((totalscale >= -0.45) and (totalscale <= 2 )) then
			if (deltascale > 0) then
				new_scale = 0.05
			elseif(deltascale < 0) then
				new_scale = -0.05
			elseif(deltascale == 0) then
				new_scale = 0
			end
	end
 
	local new_x = gameLayer:getScaleX() + new_scale
	local new_y = gameLayer:getScaleY() + new_scale
	gameLayer:setScale(new_x,new_y) 
 
 
 
 
 
	oldscale  = nscale
	totalscale = totalscale + new_scale
 
 
 
end

I am sorry for the amount of code i posted but i really cant figure it out how to deal with that pinch zoom ;D

IQ_QI · February 2013

update : fixed the math problem but eventhough i set the anchorpoint to (0.5,0.5) its still zooming in the top left corner of that sprite ? 0.0

Cyberience · March 2013

Corrct me if I am wrongm but when you pinch zoom or shrink you have to recalculate the top left corner to print it correctly, so Top left is Zero, so it would be +.5 the difference. on both X and Y.

Niicodemus · March 2013

I wrote a camera class that implements this how I think you want it. You could check it out to see how I solved this problem.

http://www.giderosmobile.com/forum/discussion/2715/camera-class-with-kinetics-and-pinch-to-zoom#Item_1

I've since completely rewritten it, but I'm waiting to release a new version until I've been able to really put it through its paces.

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