class CrImage::GrayscaleImage

• CrImage::GrayscaleImage
• CrImage::Image
• Reference
• Object

Overview

An image in Grayscale. These image types are the easiest to perform feature and information extraction from, where there is only one channel to examine, and so has methods for constructing Masks from (see #threshold below).

An RGBAImage would become a GrayscaleImage this way:

image.to_gray

Included Modules

• CrImage::Format::JPEG
• CrImage::Format::PNG
• CrImage::Format::PPM
• CrImage::Format::Save
• CrImage::Format::WebP
• CrImage::Operation::BilinearResize
• CrImage::Operation::BoxBlur
• CrImage::Operation::Brightness
• CrImage::Operation::ChannelSwap
• CrImage::Operation::Contrast
• CrImage::Operation::Crop
• CrImage::Operation::Draw
• CrImage::Operation::GaussianBlur
• CrImage::Operation::HistogramEqualize
• CrImage::Operation::HorizontalBlur
• CrImage::Operation::MaskApply
• CrImage::Operation::Pad
• CrImage::Operation::Rotate
• CrImage::Operation::VerticalBlur

Extended Modules

• CrImage::Format::Open

Defined in:

Constructors

• .from_jpeg(image_data : Bytes) : self

  Read image_data as JPEG encoded bytes

• .from_jpeg(io : IO) : self

  Construct an Image from reading in bytes from io

• .from_png(image_data : Bytes) : self

  Read image_data and PNG encoded bytes

• .from_png(io : IO) : self

  Construct an Image by reading bytes from io

• .from_ppm(image_data : Bytes) : self

  Read image_data as PPM encoded bytes

• .from_ppm(io : IO) : self

  Read bytes from io as PPM encoded

• .from_webp(image_data : Bytes) : self

  Read image_data as WebP encoded bytes

• .from_webp(io : IO) : self

  Read bytes from io as WebP encoded

• .new(red : Array(UInt8), green : Array(UInt8), blue : Array(UInt8), alpha : Array(UInt8), width : Int32, height : Int32)

  Create a GrayscaleImage from a set of color channels (delegates to RGBAImage#to_gray)

• .new(gray : Array(UInt8), alpha : Array(UInt8), width : Int32, height : Int32)
• .new(gray : Array(UInt8), width : Int32, height : Int32)

  Create a GrayscaleImage with only an Array(UInt8) (alpha channel initialized as 255 throughout)

• .new(gray : Array(UInt8), width : Int32)

  Create a GrayscaleImage with only an Array(UInt8) (alpha channel initialized as 255 throughout)

Instance Method Summary

• #<(*args, **options)
• #<(*args, **options, &)
• #<=(arg)
• #==(arg)

  Returns false (other can only be a Value here).

• #>(*args, **options)
• #>(*args, **options, &)
• #>=(arg)
• #[](x : Int32, y : Int32) : Pixel

  Return a Pixel representing this cell in the image.

• #[](channel_type : ChannelType) : Array(UInt8)

  Return the Array(UInt8) corresponding to channel_type

• #[]=(channel_type : ChannelType, channel : Array(UInt8)) : Array(UInt8)

  Set the underlying Array(UInt8) of channel_type to the new channel.

• #alpha : Array(UInt8)

  Return #alpha channel

• #alpha=(alpha : Array(UInt8))
• #blue : Array(UInt8)

  Return the "#blue" channel (returns #gray)

• #clone : GrayscaleImage

  Create a new GrayscaleImage as a copy of this one

• #cross_correlate(map : Map, *, edge_policy : EdgePolicy = EdgePolicy::Repeat) : FloatMap
• #cross_correlate(*args, **options)
• #cross_correlate(*args, **options, &)
• #cross_correlate_fft(map : Map)
• #each_channel(& : Array(UInt8), ChannelType -> Nil) : Nil

  Run provided block with the ChannelType::Gray channels and channel types.

• #each_color_channel(& : Array(UInt8), ChannelType -> Nil) : Nil

  Run provided block with the ChannelType::Gray channels and channel types.

• #gray : Array(UInt8)
• #gray=(gray : Array(UInt8))
• #green : Array(UInt8)

  Return the "#green" channel (returns #gray)

• #height : Int32

  Height of image

• #height=(height : Int32)
• #invert

  Invert grayscale pixels (replace each pixel will 255 - p for all p in @gray).

• #invert!

  Invert grayscale pixels (replace each pixel will 255 - p for all p in @gray).

• #mask_from(*args, **options)
• #mask_from(*args, **options, &)
• #mean(*args, **options)
• #mean(*args, **options, &)
• #red : Array(UInt8)

  Return the "#red" channel (returns #gray)

• #size : Int32

  Return the number of pixels this image contains

• #threshold(threshold : Int) : Mask

  Construct a simple threshold Mask containing all pixels with a UInt8 value greater than #threshold Given sample image:

• #to_a : Array(UInt8)

  Receive a copy of the underlying Array(UInt8) corresponding to the ChannelType::Gray channel

• #to_gray : GrayscaleImage

  Returns self

• #to_imap : IntMap

  Convert this image into a IntMap

• #to_map! : UInt8Map

  Convert this image into a UInt8Map.

• #to_pluto : Pluto::ImageGA
• #to_rgba(color_map : Hash(UInt8, Color), *, default : Color = Color.default) : RGBAImage

  Convert this grayscale image to an RGBA one using the provided color map.

• #to_rgba : RGBAImage

  Convert this GrayscaleImage to an RGBAImage.

• #to_stumpy : StumpyCore::Canvas
• #width : Int32

  Width of image

• #width=(width : Int32)

Constructor Detail

Instance Method Detail

def invert #

Invert grayscale pixels (replace each pixel will 255 - p for all p in @gray).

Becomes

[View source]

def invert! #

Invert grayscale pixels (replace each pixel will 255 - p for all p in @gray). Modifies self.

Becomes

[View source]

def threshold(threshold : Int) : Mask #

Construct a simple threshold Mask containing all pixels with a UInt8 value greater than #threshold Given sample image:

image
  .to_gray                       # convert color image to grayscale one
  .threshold(128)                # generate a mask using threshold operator
  .to_gray                       # convert mask to grayscale image
  .save("threshold_example.jpg") # save mask as grayscale

[View source]

def to_rgba(color_map : Hash(UInt8, Color), *, default : Color = Color.default) : RGBAImage #

Convert this grayscale image to an RGBA one using the provided color map.

The provided map should have a key for all 0-255 possible gray pixel values, otherwise the default Color will be used instead (default is black).

colors = 256.times.to_a.map { |i| {i.to_u8, CrImage::Color.random} }.to_h
gray_image.to_rgba(colors).save("to_rgba_color_map_sample.jpg")

Becomes

[View source]