R/test-images.R

In fastpng: Read and Write PNG Files with Configurable Decoder/Encoder Options

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#' Test images in various R formats
#' 
#' A nested named list of test images (300 x 200 pixels).
#' 
#' Possible image color spaces within each image type
#' \describe{
#'   \item{$gray}{Gray pixels representing intensity only}
#'   \item{$gray_alpha}{Gray pixels with an alpha channel}
#'   \item{$rgb}{RGB color image}
#'   \item{$rgba}{RGB color image with alpha channel}
#' }
#' 
#' A description of the image data within each image type
#' 
#' \describe{
#'   \item{test_image$array}{ 
#'     Arrays of numeric values in the range [0, 1]
#'     \describe{
#'       \item{$gray}{A 2D matrix}
#'       \item{$gray_alpha}{A 3D array with 2 planes i.e. \code{dim(x)[3] == 2}}
#'       \item{$rgb}{A 3D array with 3 planes i.e. \code{dim(x)[3] == 2}}
#'       \item{$rgba}{A 3D array with 4 planes i.e. \code{dim(x)[3] == 2}}
#'     }
#'   }
#'   \item{test_image$array_16bit}{ 
#'     Same as \code{test_image$array} data except values contain 16 bits of 
#'     signficant color information.
#'   }
#'   \item{test_image$array_int}{ 
#'   Arrays of integer values in the range [0, 255]
#'     \describe{
#'       \item{$gray}{A 2D matrix}
#'       \item{$gray_alpha}{A 3D array with 2 planes i.e. \code{dim(x)[3] == 2}}
#'       \item{$rgb}{A 3D array with 3 planes i.e. \code{dim(x)[3] == 2}}
#'       \item{$rgba}{A 3D array with 4 planes i.e. \code{dim(x)[3] == 2}}
#'     }
#'   }
#'   \item{test_image$array_int_16bit}{ 
#'     Same as \code{test_image$array_int} data except values are in the 
#'     range [0, 65535]
#'   }
#'   \item{test_image$raster}{ 
#'     \describe{
#'       \item{$rgb}{Raster image of color values given as hex codes \code{#RRGGBB}}
#'       \item{$rgba}{Raster image of color values given as hex codes \code{#RRGGBBAA}}
#'       \item{$named}{Raster image of color values given as R color names e.g. 'red', 'blue'}
#'     }
#'   }
#'   \item{test_image$nativeraster}{ 
#'   Integer matrix of integer values. Each 32-bit numeric value holds a
#'   packed RGBA pixel
#'     \describe{
#'       \item{$rgba}{}
#'     }
#'   }
#'   \item{test_image$indexed}{ 
#'     \describe{
#'       \item{$integer_index}{An integer matrix. Each value is an index into a
#'       separately specified color-lookup table}
#'       \item{$numeric_index}{A numeric matrix. Each value is an index into a
#'       separately specified color-lookup table}
#'       \item{$palette}{An example color palette to use with indexed images. 256 colors.}
#'     }
#'   }
#'   \item{test_image$raw}{
#'   Sequences of raw bytes with attributes specifying 'width', 'height', 'depth' 
#'   (i.e. number of colors) and 'bits' (number of bits for each color)
#'     \describe{
#'       \item{$gray}{Sequence of gray pixels i.e. GGGG}
#'       \item{$gray_alpha}{Sequence of GA pixels i.e. GAGAGA...}
#'       \item{$rgb}{Sequence of RGB pixels i.e. RGBRGBRGB...}
#'       \item{$rgba}{Sequence of RGB pixels i.e. RGBARGBARGBA...}
#'     }
#'   }
#'   \item{test_image$raw_16_bit}{ 
#'   The same as \code{test_image$raw} except each color takes 2 raw bytes.
#'   }
#' }
#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"test_image"