Implement image rotation, default value for color channels, fix bug w…

…ith alpha

spec/cr-image/operation/rotate_spec.cr

@@ -0,0 +1,46 @@
+require "../../spec_helper"
+
+Spectator.describe CrImage::Operation::Rotate, :focus do
+  include SpecHelper
+
+  specs_for_operator(rotate(45),
+    gray_hash: "b23e83666e8046bd28396b3c5d7e4c7874671cfd",
+    rgba_hash: "e21797526425cd7e9473ca479f45bbdb8e049d1e"
+  )
+
+  specs_for_operator(rotate(90),
+    gray_hash: "124795c3ed7e003750d024f610626c3b22b26206",
+    rgba_hash: "fd20c71bb52ff5a148dfcea9f4fe49ab92c80804"
+  )
+
+  specs_for_operator(rotate(-30),
+    gray_hash: "a14c40f3c480330e4ec8aa9d8441d3e08d6e3864",
+    rgba_hash: "edafe8f2472918dcdad5e72187665fcc32e14851"
+  )
+
+  specs_for_operator(rotate(45, center_x: 100, center_y: 200),
+    gray_hash: "89f91776edc2c8814d235c29d0a50eaa3f015753",
+    rgba_hash: "fb4a52471956cd6a48aee2f4470477a4b295587c"
+  )
+
+  specs_for_operator(rotate(45, center_x: 375, center_y: 250, radius: 20),
+    gray_hash: "171f3aa256a46a3aeec94cddec477ed01fdb658e",
+    rgba_hash: "ba9d444ed5f4567830d6037990231aae0f3431ca"
+  )
+
+  # specs_for_operator(crop(0, 0, 750, 500),
+  #   gray_hash: "62d6101d60ee8da38d1b9d8e809091099cec5994",
+  #   rgba_hash: "d764459f778b4839972367f78197bf9a96cd11fd"
+  # )
+
+  let(image) { gray_moon_ppm }
+
+  it "rotates" do
+    image.to_rgba
+      .draw_square(0, 0, image.width - 1, image.height - 1, CrImage::Color.random)
+      .draw_circle(375, 250, 5, CrImage::Color.of("#ff0000"), fill: true)
+      .save("original.jpg")
+      .rotate(-45, center_x: 375, center_y: 250, radius: 20, pad: true)
+      .save("rotated.jpg")
+  end
+end

src/cr-image/channel_type.cr

@@ -7,4 +7,8 @@ enum CrImage::ChannelType
   Blue
   Gray
   Alpha
+
+  def default : UInt8
+    alpha? ? 255u8 : 0u8
+  end
 end

src/cr-image/image.cr

@@ -17,13 +17,14 @@ abstract class CrImage::Image
     include Operation::Brightness
     include Operation::ChannelSwap
     include Operation::Contrast
-    include Operation::GaussianBlur
-    include Operation::HorizontalBlur
-    include Operation::VerticalBlur
     include Operation::Crop
-    include Operation::Pad
     include Operation::Draw
+    include Operation::GaussianBlur
     include Operation::HistogramEqualize
+    include Operation::HorizontalBlur
+    include Operation::Rotate
+    include Operation::Pad
+    include Operation::VerticalBlur
     include Format::Save
     extend Format::Open
 

src/cr-image/map.cr

@@ -265,14 +265,14 @@ module CrImage
       @raw.dup
     end
 
-    def pad(all : Int32 = 0, *, top : Int32 = 0, bottom : Int32 = 0, left : Int32 = 0, right : Int32 = 0, pad_type : EdgePolicy = EdgePolicy::Black) : self
+    def pad(all : Int32 = 0, *, top : Int32 = 0, bottom : Int32 = 0, left : Int32 = 0, right : Int32 = 0, pad_type : EdgePolicy = EdgePolicy::Black, pad_black_value : T = T.zero) : self
       top = top > 0 ? top : all
       bottom = bottom > 0 ? bottom : all
       left = left > 0 ? left : all
       right = right > 0 ? right : all
 
       new_width = left + width + right
-      new_raw = initial_raw_pad(pad_type, new_width, top, bottom, left, right)
+      new_raw = initial_raw_pad(pad_type, new_width, top, bottom, left, right, pad_black_value)
 
       # Now copy the original values into the new raw array at the correct locations
       height.times do |y|
@@ -299,12 +299,12 @@ module CrImage
       self.class.new(new_width, new_raw)
     end
 
-    private def initial_raw_pad(pad_type, new_width, top, bottom, left, right) : Array(T)
+    private def initial_raw_pad(pad_type, new_width, top, bottom, left, right, pad_black_value) : Array(T)
       case pad_type
-      in EdgePolicy::Black then Array(T).new((top + height + bottom) * new_width) { T.zero }
+      in EdgePolicy::Black then Array(T).new((top + height + bottom) * new_width) { pad_black_value }
       in EdgePolicy::Repeat then Array(T).new((top + height + bottom) * new_width) do |i|
         current_y = i // new_width
-        next T.zero if (current_y) < top || current_y >= (top + height)
+        next pad_black_value if (current_y) < top || current_y >= (top + height)
 
         adjusted_y = (current_y) - top
         adjusted_x = i % new_width

src/cr-image/operation/pad.cr

@@ -18,7 +18,7 @@ module CrImage::Operation::Pad
   def pad!(all : Int32 = 0, *, top : Int32 = 0, bottom : Int32 = 0, left : Int32 = 0, right : Int32 = 0, pad_type : EdgePolicy = EdgePolicy::Black) : self
     orig_width = width
     each_channel do |channel, channel_type|
-      padded = UInt8Map.new(orig_width, channel).pad(all, top: top, bottom: bottom, left: left, right: right, pad_type: pad_type)
+      padded = UInt8Map.new(orig_width, channel).pad(all, top: top, bottom: bottom, left: left, right: right, pad_type: pad_type, pad_black_value: channel_type.default)
       self[channel_type] = padded.raw
       @width = padded.width
       @height = padded.height

src/cr-image/operation/rotate.cr

@@ -0,0 +1,43 @@
+module CrImage::Operation::Rotate
+  def rotate(degrees : Float64, *, center_x : Int32 = width // 2, center_y : Int32 = height // 2, radius : Int32 = -1, pad : Bool = false) : self
+    clone.rotate!(degrees, center_x: center_x, center_y: center_y, radius: radius, pad: pad)
+  end
+
+  def rotate!(degrees : Float64, *, center_x : Int32 = width // 2, center_y : Int32 = height // 2, radius : Int32 = -1, pad : Bool = false) : self
+    # TODO: use pad
+
+    # Rotate backwards, so that we can "look back" from the output pixel location into the input pixel location
+    radians = -Math::PI * degrees / 180
+    sin = Math.sin(radians)
+    cos = Math.cos(radians)
+    radius_sq = radius * radius
+
+    new_size = size
+    out_center_x = center_x
+    out_center_y = center_y
+    each_channel do |channel, channel_type|
+      new_x = -1
+      new_y = -1
+      new_channel = Array.new(new_size) do |i|
+        new_x += 1
+        new_x %= width
+        new_y += 1 if new_x == 0
+
+        if radius >= 0
+          next channel[i] if ((new_x - center_x) ** 2 + (new_y - center_y) ** 2) > radius_sq
+        end
+
+        orig_x = (cos * (new_x - center_x) - sin * (new_y - center_y) + out_center_x).round.to_i
+        orig_y = (sin * (new_x - center_x) + cos * (new_y - center_y) + out_center_y).round.to_i
+
+        next channel_type.default if orig_x < 0 || orig_x >= width || orig_y < 0 || orig_y >= height
+
+        channel.unsafe_fetch(orig_y * width + orig_x)
+      end
+
+      self[channel_type] = new_channel
+    end
+
+    self
+  end
+end

src/cr-image/rgba_image.cr

@@ -89,6 +89,11 @@ class CrImage::RGBAImage < CrImage::Image
     )
   end
 
+  # Returns self
+  def to_rgba : RGBAImage
+    self
+  end
+
   # Return the number of pixels in this image
   def size : Int32
     @width * @height

src/lib-formats/jpeg.cr

@@ -45,10 +45,10 @@ module CrImage::Format::JPEG
       )
       check_jpeg handle, LibJPEGTurbo.destroy(handle)
 
-      red = Array.new(width * height) { 0u8 }
-      green = Array.new(width * height) { 0u8 }
-      blue = Array.new(width * height) { 0u8 }
-      alpha = Array.new(width * height) { 255u8 }
+      red = Array.new(width * height) { ChannelType::Red.default }
+      green = Array.new(width * height) { ChannelType::Green.default }
+      blue = Array.new(width * height) { ChannelType::Blue.default }
+      alpha = Array.new(width * height) { ChannelType::Alpha.default }
 
       (width * height).times do |index|
         red.unsafe_put(index, buffer[index * 3])