What happens when you create a PNG with and without sRGB or linear RGB colorspace headers?

PNG colorspace experiments

## Make a 5 pixel gradient PNG with no header: 0, 64, 128, 191, 255.
## Save the values with PIL (Python Image Library). PIL does not store a header.
python make_png.py
'''
from numpy import *
from PIL import Image

N = 5
arr = zeros( (1,N,3) )
arr[:] = linspace(0,1,N)[newaxis,:,newaxis]

Image.fromarray( (arr*255).round().clip(0,255).astype(uint8) ).save( "test.png" )
'''

## Use ImageMagick to assign an sRGB header
convert test.png -set colorspace sRGB -define png:color-type=2 test_sRGB.png
## Use ImageMagick to assign a linear RGB header
convert test.png -set colorspace RGB -define png:color-type=2 test_RGB.png

## Print the values after loading with PIL (Python Image Library). PIL ignores the header
## and gives us the same raw values:
python print_png.py test.png
python print_png.py test_sRGB.png
python print_png.py test_RGB.png
'''
from numpy import *
from PIL import Image
import sys

arr = asarray( Image.open( sys.argv[1] ) )
print( arr )
'''

## Open the images with Preview. Preview on OS X 10.11.6 ignores the colorspace when showing images. Using a color picker confirms this.
open test.png
open test_sRGB.png
open test_RGB.png

## With Safari, all three look the same in http://yig.github.io/image-rgb-in-3D/
## Safari is ignoring headers.
## With Chrome, the RGB one looks different http://yig.github.io/image-rgb-in-3D/
## Chrome does not ignore headers and converts values to sRGB for pixel
## values in JavaScript.

## Check the metadata.
## The original has nothing:
exiftool test.png
## sRGB is full of information (gamma, white point, red, green, and blue X Y):
exiftool test_sRGB.png
## Linear RGB has gamma = 1:
exiftool test_RGB.png 

## Use ImageMagick to convert to sRGB. This does nothing because ImageMagick assumes sRGB
## for a PNG with no header.
convert test.png -colorspace sRGB -define png:color-type=2 test_colorspace_sRGB.png
python print_png.py test_colorspace_sRGB.png

## Use ImageMagick to convert to RGB. This changes all the values stored in the image by
## applying inverse gamma correction, because ImageMagick assumes sRGB.
convert test.png -colorspace RGB -define png:color-type=2 test_colorspace_RGB.png
python print_png.py test_colorspace_RGB.png