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###
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  Loads an image and gives access to pixel data.
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  @class bkcore.ImageData
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  @author Thibaut 'BKcore' Despoulain <http://bkcore.com>
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###
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class ImageData
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  ###
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    Creates a new ImageData object
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    @param path string The path of the image
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    @param callback function A callback function to be called
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      once th eimage is loaded
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  ###
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  constructor: (path, callback)->
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    @image = new Image
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    @pixels = null
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    @canvas = null
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    @loaded = false
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    @image.onload = ()=>
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      @canvas = document.createElement('canvas')
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      @canvas.width = @image.width
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      @canvas.height = @image.height
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      context = @canvas.getContext('2d')
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      context.drawImage(@image, 0, 0)
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      @pixels = context.getImageData(0,0, @canvas.width, @canvas.height)
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      @loaded = true
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      context = null
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      @canvas = null
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      @image = null
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      callback?.call(@)
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    @image.crossOrigin = "anonymous"
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    @image.src = path
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  ###
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    Gets pixel RGBA data at given index
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    @param x int In pixels
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    @param y int In pixels
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    @return Object{r,g,b,a}
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  ###
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  getPixel: (x, y)->
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    if !@pixels? or x < 0 or y < 0 or x >= @pixels.width or y >= @pixels.height
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      return {r: 0, g: 0, b:0, a:0}
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    i = (y*@pixels.width + x) * 4
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    return {
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      r: @pixels.data[i]
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      g: @pixels.data[i+1]
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      b: @pixels.data[i+2]
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      a: @pixels.data[i+3]
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    }
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  ###
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    Gets pixel RGBA data at given float index using bilinear interpolation
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    @param x float In subpixels
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    @param y float In subpixels
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    @return Object{r,g,b,a}
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  ###
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  getPixelBilinear: (fx, fy)->
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    x = Math.floor(fx)
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    y = Math.floor(fy)
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    rx = fx - x - .5
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    ry = fy - y - .5
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    ax = Math.abs(rx)
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    ay = Math.abs(ry)
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    dx = if rx < 0 then -1 else 1
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    dy = if ry < 0 then -1 else 1
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    c = @getPixel(x, y)
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    cx = @getPixel(x+dx, y)
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    cy = @getPixel(x, y+dy)
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    cxy = @getPixel(x+dx, y+dy)
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    cf1 = [
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      (1-ax) * c.r + ax * cx.r
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      (1-ax) * c.g + ax * cx.g
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      (1-ax) * c.b + ax * cx.b
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      (1-ax) * c.a + ax * cx.a
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    ]
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    cf2 = [
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      (1-ax) * cy.r + ax * cxy.r
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      (1-ax) * cy.g + ax * cxy.g
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      (1-ax) * cy.b + ax * cxy.b
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      (1-ax) * cy.a + ax * cxy.a
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    ]
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    return {
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      r: (1-ay) * cf1[0] + ay * cf2[0]
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      g: (1-ay) * cf1[1] + ay * cf2[1]
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      b: (1-ay) * cf1[2] + ay * cf2[2]
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      a: (1-ay) * cf1[3] + ay * cf2[3]
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    }
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  ###
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    Gets pixel data at given index
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    as 3-bytes integer (for floating-point textures erzats, from RGB values)
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    @param x int In pixels
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    @param y int In pixels
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    @return int (R + G*255 + B*255*255)
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  ###
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  getPixelF: (x, y)->
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    c = @getPixel(x, y)
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    return c.r + c.g * 255 + c.b * 255 * 255
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  ###
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    Gets pixel data at given float index using bilinear interpolationas
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    as 3-bytes integer (for floating-point textures erzats, from RGB values)
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    @param x float In subpixels
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    @param y float In subpixels
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    @return Object{r,g,b,a}
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  ###
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  getPixelFBilinear: (fx, fy)->
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    c = @getPixelBilinear(fx, fy)
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    return c.r + c.g * 255 + c.b * 255 * 255
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###
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  Exports
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  @package bkcore
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###
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exports = exports ? @
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exports.bkcore ||= {}
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exports.bkcore.ImageData = ImageData
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