Data commit

Task/Grayscale-image/Nim/grayscale-image.nim

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+import bitmap
+import lenientops
+
+type
+
+  GrayImage* = object
+    w*, h*: Index
+    pixels*: seq[Luminance]
+
+proc newGrayImage*(width, height: int): GrayImage =
+  ## Create a gray image with given width and height.
+  new(result)
+  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: GrayImage; x, y: int; lum: Luminance) =
+  ## Set a pixel luminance to given value.
+  img.pixels[y * img.w + x] = lum
+
+proc fill*(img: 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 = newGrayImage(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 = newImage(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 = newImage(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")