Article Tutorials/Drawing Bitmaps

Displaying Images

First we need to add images to our project:

Right-click Files and select Link existing files from the menu:

Add in an image you’ve created or downloaded from the internet:

You can copy my yinyang image from here:

Now we can display this image on the screen.

In your main.lua:

local yinyang = Bitmap.new(Texture.new("yinyang.png"))
yinyang:setX(200)
yinyang:setY(200)
stage:addChild(yinyang)

Launch the Player and press the Play button to see the result:

You can also use SetPosition:

yinyang:setPosition(210, 220)

Now set the size (scale) of the image. X-scale to ½ the width and Y-scale to twice the height:

yingyang:setScale(0.5, 2)

You can flip your image horizontally or vertically in code to save creating separate images for each direction:

yingyang:setScaleX(-1)
yingyang:setScaleY(-1)

Change your image rotation angle:

yinyang:setRotation(45)

Fade your image. This sets its transparency:

yinyang:setAlpha(0.5) -- Alpha can be anywhere from 0 to 1

You can also make your image totally disappear without removing it from the stage:

yinyang:setVisible(false)

When you’re finished with your image, don’t forget to remove it from the stage so it won’t take up memory and processor:

stage:removeChild(yinyang)

Remove your image from memory totally:

yinyang = nil

Sprite Group

You can add a few images to a Sprite group object, then all transformation done on the group will propagate to its children:

spritegroup = Sprite.new()
spritegroup:setPosition(100,100)
local yinyang = Bitmap.new(Texture.new("yinyang.png"))
yinyang:setPosition(10,10)
spritegroup:addChild(yinyang)
local yinyang2 = Bitmap.new(Texture.new("yinyang.png"))
yinyang2:setPosition(100,100)
spritegroup:addChild(yinyang2)
stage:addChild(spritegroup)

Set all images in the Sprite group to half transparency:

spritegroup:setAlpha(0.5)

Rotate the Sprite group to rotate all images:

spritegroup:setRotation(45)

Note: this tutorial was written by Jason Oakley and was originally available at: http://bluebilby.com/2013/04/14/gideros-mobile-tutorial-displaying-images

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