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Grayscale image: Difference between revisions
→{{header|MATLAB}}
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<lang Matlab>function [grayImage] = colortograyscale(inputImage)
grayImage = rgb2gray(inputImage);</lang>
=={{header|Nim}}==
The right way to proceed would have been to add the case of gray scale images to our Image type (using a “variant object” with a discriminator). But we didn’t want to change the Image type, so we have created a GrayImage type and duplicated most procedures.
<lang Nim>
import bitmap
import lenientops
type
GrayImage* = object
w*, h*: Index
pixels*: seq[Luminance]
proc initGrayImage*(width, height: int): GrayImage =
## Create a gray image with given width and height.
result.w = width
result.h = height
result.pixels.setLen(width * height)
iterator indices*(img: GrayImage): Point =
## Yield the pixels coordinates as tuples.
for y in 0 ..< img.h:
for x in 0 ..< img.w:
yield (x, y)
proc `[]`*(img: GrayImage; x, y: int): Luminance =
## Get a pixel luminance value.
img.pixels[y * img.w + x]
proc `[]=`*(img: var GrayImage; x, y: int; lum: Luminance) =
## Set a pixel luminance to given value.
img.pixels[y * img.w + x] = lum
proc fill*(img: var GrayImage; lum: Luminance) =
## Set the pixels to a given luminance.
for x, y in img.indices:
img[x, y] = lum
func toGrayLuminance(color: Color): Luminance =
## Compute the luminance from RGB value.
Luminance(0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b + 0.5)
func toGrayImage*(img: Image): GrayImage =
##
result = initGrayImage(img.w, img.h)
for pt in img.indices:
result[pt.x, pt.y] = img[pt.x, pt.y].toGrayLuminance()
func toImage*(img: GrayImage): Image =
result = initImage(img.w, img.h)
for pt in img.indices:
let lum = img[pt.x, pt.y]
result[pt.x, pt.y] = (lum, lum, lum)
#———————————————————————————————————————————————————————————————————————————————————————————————————
when isMainModule:
import ppm_write
# Create a RGB image.
var image = initImage(100, 50)
image.fill(color(128, 128, 128))
for row in 10..20:
for col in 0..<image.w:
image[col, row] = color(0, 255, 0)
for row in 30..40:
for col in 0..<image.w:
image[col, row] = color(0, 0, 255)
# Convert it to grayscale.
var grayImage = image.toGrayImage()
# Convert it back to RGB in order to save it in PPM format using the available procedure.
var convertedImage = grayImage.toImage()
convertedImage.writePPM("output_gray.ppm")</lang>
=={{header|OCaml}}==
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