class

CrImage::NYCbCrA

Inherits CrImage::Image / Reference / Object

NYCbCrA is an in-memory image using Y'CbCr color space with alpha channel.

Similar to YCbCr but includes an alpha channel for transparency. The alpha values are non-premultiplied, meaning color values are independent of the alpha value.

Example:

img = CrImage::NYCbCrA.new(
  CrImage.rect(0, 0, 640, 480),
  CrImage::YCbCrSubSampleRatio::YCbCrSubsampleRatio420
)

Constructors

new(rect : Rectangle, sub_sample_ratio : YCbCrSubSampleRatio)

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new(y : Slice(UInt8) = Bytes.empty, cb : Slice(UInt8) = Bytes.empty, cr : Slice(UInt8) = Bytes.empty, a : Slice(UInt8) = Bytes.empty, y_stride : Int32 = 0, c_stride : Int32 = 0, a_stride : Int32 = 0, sub_sample_ratio : CrImage::YCbCrSubSampleRatio = YCbCrSubSampleRatio::YCbCrSubsampleRatio444, rect : CrImage::Rectangle = Rectangle.zero)

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Instance methods

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a=(a : Bytes)

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a_offset(x, y)

returns the index of the first element of a that corresponds to the pixel at (x,y)

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a_stride

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a_stride=(a_stride : Int32)

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at(x : Int32, y : Int32) : Color::Color

Returns the color of the pixel at (x,y).

If coordinates are outside bounds, returns a default color (typically transparent black) rather than raising an exception. This simplifies image processing algorithms.

at(bounds().min.x, bounds().min.y) returns the upper-left pixel of the grid.
at(bounds().max.x-1, bounds().max.y-1) returns the lower-right one.

For explicit nil on out-of-bounds, concrete types provide at? method.

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bounds

bounds returns the domain for which at can return non-zero color. The bounds do not necessarily contain the point(0,0).

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c_offset(x, y)

returns the index of the first element of cb or cr that corresponds to the pixel at (x,y)

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c_stride

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c_stride=(c_stride : Int32)

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cb=(cb : Bytes)

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color_model

color_model returns the Image's color model

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cr=(cr : Bytes)

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nycbcra_at(x : Int32, y : Int32) : Color::Color

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opaque?

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rect

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rect=(rect : Rectangle)

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set(x : Int32, y : Int32, c : Color::Color)

Sets the color of the pixel at (x,y).

If the provided coordinates are not within bounds, this method does nothing (no-op). This simplifies drawing operations that may extend beyond image boundaries.

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set_nycbcra(x : Int32, y : Int32, c : Color::NYCbCrA)

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sub_image(r : Rectangle) : Image

sub_image returns an image representing the portion of the image visible though r. the returned value shares pixes with the original image.

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sub_sample_ratio

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sub_sample_ratio=(sub_sample_ratio : YCbCrSubSampleRatio)

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y=(y : Bytes)

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