Scaling a table

Solar2D Lua Language
#1

Hey folks,

Is there a Lua or Corona-built-in way to scale a table of values?

I have a table of vertices that I will use with display.newPolygon.

This table is normalized so that all values are between 0 and 1.

I’ll give you an example of a normalized set of vertices that make a star.

local vertices = { 0.5, 0, 0.63, 0.36, 1, 0.4, 0.73, 0.6, 0.81, 1, 0.5, 0.8, 0.19, 1, 0.27, 0.6, 0, 0.4, 0.37, 0.36 }

This set can now have it’s values multiplied by a given scalar (such as the width or height of a frame) so that it is set to that size.

How should I go about multiplying these values?

#2

I’ve resorted to looping through the table and multiplying the values one by one (code below). If anyone has a better solution, please post it.

local scalar = 50 --lets make a star 50 pixels wide and high for i = 1, #vertices do vertices[i] = vertices[i] \* scalar; end

I suppose you could modify it so that every second vertex is multiplied by another scalar so you could have scalarX and scalarY for more control.

#3

If you are looking to just change the size of the star you can use myStar.xScale and myStar.yScale.  Or I may just not be understanding what you need…

#4

Thank you, that’s exactly what I needed.

I believe the docs need some updating; I didn’t know polygon had an x/yScale modifier.

Even ShapeObject docs doesn’t mention it, nor does the guide on Creating Shapes.

It seems like rect has a rect:scale(x,y) function but it doesn’t work for shapes.

#5

I agree that the docs could be a little improved.  However on the ShapeObjects page under Properties it does state that it inherits properties of DisplayObject, which does show you all of the available functions.  Though I admit this is a little tedious to get to. 

#6

Ah thanks JonPM. I guess I just had to keep following the parent. Knowing that will make my life much easier :slight_smile:

#7

I’ve resorted to looping through the table and multiplying the values one by one (code below). If anyone has a better solution, please post it.

local scalar = 50 --lets make a star 50 pixels wide and high for i = 1, #vertices do vertices[i] = vertices[i] \* scalar; end

I suppose you could modify it so that every second vertex is multiplied by another scalar so you could have scalarX and scalarY for more control.

#8

If you are looking to just change the size of the star you can use myStar.xScale and myStar.yScale.  Or I may just not be understanding what you need…

#9

Thank you, that’s exactly what I needed.

I believe the docs need some updating; I didn’t know polygon had an x/yScale modifier.

Even ShapeObject docs doesn’t mention it, nor does the guide on Creating Shapes.

It seems like rect has a rect:scale(x,y) function but it doesn’t work for shapes.

#10

I agree that the docs could be a little improved.  However on the ShapeObjects page under Properties it does state that it inherits properties of DisplayObject, which does show you all of the available functions.  Though I admit this is a little tedious to get to. 

#11

Ah thanks JonPM. I guess I just had to keep following the parent. Knowing that will make my life much easier :slight_smile: