Scrupp: Image handling

Image support is implemented using SDL_image.

JPEG support requires the JPEG library:: IJG Homepage
PNG support requires the PNG library:: PNG Homepage
and the Zlib library:: Zlib Homepage
TIFF support requires the TIFF library:: SGI TIFF FTP Site

Loading

scrupp.addImage(filename): Loads the image file with the given filename. Supported formats: BMP, PNM (PPM/PGM/PBM), XBM, LBM, PCX, GIF, JPEG, PNG and TIFF. Returns an image object.

Methods

image:getWidth(): Returns the image width.
image:getHeight(): Returns the image height.
image:getSize(): Returns the width and the height of the image.
image:isTransparent(x, y): Returns true if the pixel of the image with the coordinates x and y is not opaque, i.e. has an alpha value lower than 255. Returns false otherwise. This is not influenced by the alpha value of the whole image changed using image:setAlpha().
image:setAlpha(alpha): Changes the alpha value of the image. alpha has to be between 0 (transparent) and 255 (opaque).
image:getAlpha(): Returns the current alpha value of the image. This value is between 0 (transparent) and 255 (opaque).
image:render(x, y): Renders the image at the window coordinates x and y.
image:render(table): This is nearly the same as the last one. This time a table contains the arguments. It's complete structure follows.
table = { x, -- x-coordinate of the image position -- mandatory y, -- y-coordinate of the image position -- mandatory centerX = [x-coordinate of the center for positioning, scaling and rotation], centerY = [y-coordinate of the center for positioning, scaling and rotation], scaleX = [scale factor for the x-axis], scaleY = [scale factor for the y-axis], rotate = [angle in degrees to rotate the image], rect = { x, y, width, height }, -- optional color = { red, green, blue, alpha } -- optional }
The first two elements of the array part of the table have to be the x- and y-coordinate of the point that the image should be rendered at. The table may have an optional rect entry. This has to be a table describing the rectangle the image should be clipped to. It contains the x- and y-coordinate of the upper left corner and the width and height of the rectangle inside the image. The entries centerX and centerY are optional and default to zero, the left-upper corner of the image. scaleX and scaleY are optional as well and default to one. rotate has a default value of zero dregrees and is optional, too. The optional color entry is a table defining some kind of color filter. If you have a grayscale image, it will be colorized with this color. As always the table looks like this: {red, green, blue, [alpha]} with each value between 0 and 255.

Example

scrupp.init("Image Test", 600, 400, 32, false)

-- load an image file
local image = scrupp.addImage("path_to_image_file")

-- get the dimension of the image
local width = image:getWidth()
local height = image:getHeight()

-- this has the same result:
local width, height = image:getSize()

if width > scrupp.getWindowWidth() or height > scrupp.getWindowHeight() then
	print("Please choose an image with smaller dimensions.")
	scrupp.exit()
end

-- calculate the x- and y-coordinate of the image
local x = (scrupp.getWindowWidth()-width)/2
local y = (scrupp.getWindowHeight()-height)/2

main = {
	render = function(dt)
		-- get the position of the mouse pointer
		mx, my = mouse:getPos()
		-- set the image alpha depending on the x-coordinate of the 
		-- mouse pointer
		image:setAlpha(mx/scrupp.getWindowWidth()*200+50)
		-- if you click with the left mouse button,
		-- only a part of the image is rendered
		if mouse.isDown("left") then
			image:render{
				mx, my,
				rect = { mx-x, my-y, width/2, height/2 }
			}
		-- otherwise the whole image is rendered
		else
			image:render(x,y)
		end
	end
}