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Bitmap/Histogram: Difference between revisions
→{{header|Mathematica}}
Thundergnat (talk | contribs) (→{{header|Raku}}: Fix up some internal links) |
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ImageLevels[img];
</lang>
=={{header|Nim}}==
<lang Nim>import bitmap
import grayscale_image
type Histogram = array[Luminance, Natural]
#---------------------------------------------------------------------------------------------------
func histogram*(img: GrayImage): Histogram =
## Build and return gray scale image histogram.
for lum in img.pixels:
inc result[lum]
#---------------------------------------------------------------------------------------------------
func median*(hist: Histogram): Luminance =
# Return the median luminance of a histogram.
var
inf = byte(0)
sup = Luminance.high
infCount, supCount = 0
while inf != sup:
if infCount < supCount:
inc infCount, hist[inf]
inc inf
else:
inc supCount, hist[sup]
dec sup
result = inf
#———————————————————————————————————————————————————————————————————————————————————————————————————
when isMainModule:
import ppm_read, ppm_write
# Read an image.
let image = readPPM("house.ppm")
# Build its histogram and find the median luminance.
let grayImage = image.toGrayImage
let hist = grayImage.histogram()
let m = hist.median()
echo "Median luminance: ", m
# Convert to black and white.
for pt in image.indices:
image[pt.x, pt.y] = if grayImage[pt.x, pt.y] < m: Black else: White
# Save image as a PPM file.
image.writePPM("house_bw.ppm")</lang>
=={{header|OCaml}}==
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