Various scaling and moving operations are available for images. You can scale an image proportionally by a percentage, scale it to fit proportionally within a bounding box, or scale width and height to fit exactly within a bounding box.

#!/usr/local/bin/macruby

framework 'cocoa'
require 'rubygems'
require 'hotcocoa/graphics'
include HotCocoa
include Graphics

# set up the canvas and font
canvas = Canvas.new :type => :image, :filename => 'moving.png', :size => [400,400]
canvas.background Color.white
canvas.font 'Skia'
canvas.fontsize 14
canvas.fill Color.black
canvas.stroke Color.red

# load an image
img = Image.new 'v2.jpg'

# SCALE (multiply both dimensions by a scaling factor)
img.scale(0.2)
canvas.draw(img,0,240)  # draw the image at the specified coordinates
canvas.text("scale to 20%",0,220)

# FIT (scale to fit within the given dimensions, maintaining original aspect ratio)
img.reset               # first reset the image to its original size
img.fit(100,100)
canvas.fill(Color.white)
canvas.rect(120,240,100,100)
canvas.fill(Color.black)
canvas.draw(img,133,240)
canvas.text("fit into 100x100",120,220)

# RESIZE (scale to fit exactly within the given dimensions)
img.reset
img.resize(100,100)
canvas.draw(img,240,240)
canvas.text("resize to 100x100",240,220)

# CROP (to the largest square containing image data)
img.reset
img.scale(0.2).crop
canvas.draw(img,0,100)
canvas.text("crop max square",0,80)

# CROP (within a rectangle starting at x,y with width,height)
img.reset
img.scale(0.3).crop(0,0,100,100)
canvas.draw(img,120,100)
canvas.text("crop to 100x100",120,80)

# ROTATE
img.origin(:center)
img.rotate(45)
canvas.draw(img,300,140)
canvas.text("rotate 45 degrees",250,50)

#img.origin(:center)   # center the image
#img.translate(0,-150)    # move the image

canvas.save

You can apply various Photoshop-style filters to images, then render them to the canvas.

#!/usr/local/bin/macruby

framework 'cocoa'
require 'rubygems'
require 'hotcocoa/graphics'
include HotCocoa
include Graphics

# set up the canvas and font
canvas = Canvas.new :type => :image, :filename => 'effects.png', :size => [400,400]
canvas.background(Color.white)
canvas.font('Skia')
canvas.fontsize(14)
canvas.fill(Color.black)

# load image file
img = Image.new('v2.jpg')

# set image width/height, starting position, and increment position
w,h = [100,100]
x,y = [0,290]
xoffset = 105
yoffset = 130

# ORIGINAL image, resized to fit within w,h:
img.fit(w,h)
canvas.draw(img,x,y)
canvas.text("original",x,y-15)
x += xoffset

# CRYSTALLIZE: apply a "crystallize" effect with the given radius
img.reset.fit(w,h)
img.crystallize(5.0)
canvas.draw(img,x,y)
canvas.text("crystallize",x,y-15)
x += xoffset

# BLOOM: apply a "bloom" effect with the given radius and intensity
img.reset.fit(w,h)
img.bloom(10, 1.0)
canvas.draw(img,x,y)
canvas.text("bloom",x,y-15)
x += xoffset

# EDGES: detect edges
img.reset.fit(w,h)
img.edges(10)
canvas.draw(img,x,y)
canvas.text("edges",x,y-15)
x += xoffset

# (go to next row)
x = 0
y -= yoffset

# POSTERIZE: reduce image to the specified number of colors
img.reset.fit(w,h)
img.posterize(8)
canvas.draw(img,x,y)
canvas.text("posterize",x,y-15)
x += xoffset

# TWIRL: rotate around x,y with radius and angle
img.reset.fit(w,h)
img.twirl(35,50,40,90)
canvas.draw(img,x,y)
canvas.text("twirl",x,y-15)
x += xoffset

# EDGEWORK: simulate a woodcut print
img.reset.fit(w,h)
canvas.rect(x,y,img.width,img.height) # needs a black background
img.edgework(0.5)
canvas.draw(img,x,y)
canvas.text("edgework",x,y-15)
x += xoffset

# DISPLACEMENT: use a second image as a displacement map
img.reset.fit(w,h)
img2 = Image.new('italy.jpg').resize(img.width,img.height)
img.displacement(img2, 30.0)
canvas.draw(img,x,y)
canvas.text("displacement",x,y-15)
x += xoffset

# (go to next row)
x = 0
y -= yoffset

# DOTSCREEN: simulate a dot screen: center point, angle(0-360), width(1-50), and sharpness(0-1)
img.reset.fit(w,h)
img.dotscreen(0,0,45,5,0.7)
canvas.draw(img,x,y)
canvas.text("dotscreen",x,y-15)
x += xoffset

# SHARPEN: sharpen using the given radius and intensity
img.reset.fit(w,h)
img.sharpen(2.0,2.0)
canvas.draw(img,x,y)
canvas.text("sharpen",x,y-15)
x += xoffset

# BLUR: apply a gaussian blur with the given radius
img.reset.fit(w,h)
img.blur(3.0)
canvas.draw(img,x,y)
canvas.text("blur",x,y-15)
x += xoffset

# MOTION BLUR: apply a motion blur with the given radius and angle
img.reset.fit(w,h)
img.motionblur(10.0,90)
canvas.draw(img,x,y)
canvas.text("motion blur",x,y-15)
x += xoffset

# save the canvas
canvas.save

You can apply various color adjustments to a loaded image, then render it to the canvas.  You can also grab colors from an image for use in a gradient or to paint objects on the canvas.

#!/usr/local/bin/macruby

framework 'cocoa'
require 'rubygems'
require 'hotcocoa/graphics'
include HotCocoa
include Graphics

# set up the canvas and font
canvas = Canvas.new :type => :image, :filename => 'colors.png', :size => [400,400]
canvas.background(Color.white)
canvas.font('Skia')
canvas.fontsize(14)
canvas.fill(Color.black)

# LOAD IMAGE
img = Image.new('v2.jpg')

w,h = [100,100]
x,y = [0,290]
xoffset = 105
yoffset = 130

# ORIGINAL image, resized to fit within w,h:
img.fit(w,h)
canvas.draw(img,x,y)
canvas.text("original",x,y-15)
x += xoffset

# HUE: rotate color wheel by degrees
img.reset.fit(w,h)
img.hue(45)
canvas.draw(img,x,y)
canvas.text("hue",x,y-15)
x += xoffset

# EXPOSURE: increase/decrease exposure by f-stops
img.reset.fit(w,h)
img.exposure(1.0)
canvas.draw(img,x,y)
canvas.text("exposure",x,y-15)
x += xoffset

# SATURATION: adjust saturation by multiplier
img.reset.fit(w,h)
img.saturation(2.0)
canvas.draw(img,x,y)
canvas.text("saturation",x,y-15)
x += xoffset

# (go to next row)
x = 0
y -= yoffset

# CONTRAST: adjust contrast by multiplier
img.reset.fit(w,h)
img.contrast(2.0)
canvas.draw(img,x,y)
canvas.text("contrast",x,y-15)
x += xoffset

# BRIGHTNESS: adjust brightness
img.reset.fit(w,h)
img.brightness(0.5)
canvas.draw(img,x,y)
canvas.text("brightness",x,y-15)
x += xoffset

# MONOCHROME: convert to a monochrome image
img.reset.fit(w,h)
img.monochrome(Color.orange)
canvas.draw(img,x,y)
canvas.text("monochrome",x,y-15)
x += xoffset

# WHITEPOINT: remap the white point
img.reset.fit(w,h)
img.whitepoint(Color.whiteish)
canvas.draw(img,x,y)
canvas.text("white point",x,y-15)
x += xoffset

# (go to next row)
x = 0
y -= yoffset

# CHAINING: apply multiple effects at once
img.reset.fit(w,h)
img.hue(60).saturation(2.0).contrast(2.5)
canvas.draw(img,x,y)
canvas.text("multi effects",x,y-15)
x += xoffset

# COLORS: sample random colors from the image and render as a gradient
img.reset.fit(w,h)              # reset the image and scale to fit within w,h
colors = img.colors(10).sort!   # select 10 random colors and sort by brightness
gradient = Gradient.new(colors) # create a new gradient using the selected colors
rect = Path.new.rect(x,y,img.width,img.height) # create a rectangle the size of the image
canvas.beginclip(rect)          # begin clipping so the gradient will only fill the rectangle
canvas.gradient(gradient,x,y,x+img.width,y+img.height) # draw the gradient between opposite corners of the rectangle
canvas.endclip                  # end clipping so we can draw on the rest of the canvas
canvas.text("get colors",x,y-15)    # add text label
x += xoffset

canvas.save

You can use various Photoshop-style blend modes to composite two or more images by applying the “blend” method to an Image object.

#!/usr/local/bin/macruby

require 'hotcocoa/graphics'
include HotCocoa
include Graphics

# set up the canvas and font
canvas = Canvas.new :type => :image, :filename => 'blend.png', :size => [400,730]
canvas.background(Color.white)
canvas.font('Skia')
canvas.fontsize(14)

# set image width,height
w,h = [95,95]

# set initial drawing position
x,y = [0,canvas.height - h - 10]

# load and resize two images
imgA = Image.new('v2.jpg').resize(w,h)
imgB = Image.new('italy.jpg').resize(w,h)

# add image B to image A using each blending mode, and draw to canvas
for blendmode in [:normal,:multiply,:screen,:overlay,:darken,:lighten,
  :colordodge,:colorburn,:softlight,:hardlight,:difference,:exclusion,
  :hue,:saturation,:color,:luminosity,:maximum,:minimum,:add,:atop,
  :in,:out,:over] do
  imgA.reset.resize(w,h)
  imgA.blend(imgB, blendmode)
  canvas.draw(imgA,x,y)
  canvas.text(blendmode,x,y-15)
  x += w + 5
  if (x > canvas.width - w + 5)
    x = 0
    y -= h + 25
  end
end

canvas.save