Solve It
There are many ways you could create a filter with a red hue. One way is to consider the overall brightness of a pixel and map it to the same brightness on a red-hue scale. This red scale has white and black at 100% brightness and 0% brightness respectively, but in the middle, where the grayscale color would be rgb(128,128,128), this scale has a red color rgb(255,0,0). You can see that the red (R) value increases with brightness up to 50%, then it stays 255. Green (G) and blue (B) values are zero up to 50% and then increase to 255 at 100%.
Code It
function filterRed(image) {
for (var pixel of image.values()) {
var avg = (pixel.getRed() + pixel.getGreen() + pixel.getBlue()) / 3;
if (avg < 128) {
pixel.setRed(2 * avg);
pixel.setGreen(0);
pixel.setBlue(0);
} else {
pixel.setRed(255);
pixel.setGreen(2 * avg - 255);
pixel.setBlue(2 * avg - 255);
}
}
}
var img = new SimpleImage("chapel.png");
filterRed(img);
print (img);
See It
Available Images
chapel.png
[231x308]
rodger.png
[315x424]
astrachan.jpg
[240x360]
duvall.jpg
[200x300]
hilton.jpg
[140x210]
lion.jpg
[250x188]
Drop your images onto the area above to make it available within your code editor on this page. Note: your images will not be uploaded anywhere, they will stay on your computer.
