Roy - Colour Correction

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What does Roy do?

Roy is the new name for Huey. Roy is a colour correction/adjustment plug-in that allows spot colour to be corrected -- that is, for image areas of one colour or a range of similar colours to be adjusted for tint, brightness and overall saturation. Roy has three channels of colour correction -- Red, Green and Blue -- each of which can be adjusted along a wide range of similar hues, allowing all image colours to be selected and modified.

Download Freeware Now

Windows/Mac/Linux production release available now.
Windows, Linux and Mac versions included in the same download. Read the Roy Release Notes, then access the download area.
You'll find installation instructions as INSTALL.txt in the zipfile.
Please provide feedback at the email address above.

Purchase RoyPRO Professional Version Now

Windows, Linux and Mac versions included in the same download. RoyPRO now available for Windows, Macintosh (Intel and PPC), and Linux. RoyPRO gives you three extra channels of colour correction (cyan, magenta and yellow), and enhances how colours are selected for modification. Each channel gains a "width" slider which allows you to adjust the span of colours that are selected and a "softness" slider which allows you to change the feathering of the selection from a hard cutoff to a very wide, gentle slope. Roy Freeware has these values fixed to useful and flexible constants, but it is often helpful to change them when attempting for precise colour correction.

RoyPRO: $10 USD

Already purchased, but need an upgrade? Click Here.

Sample Output

Roy Car - Before Info

Roy Car - After Info

Restore Me Now

Mostly just playing around. I gave the car a rust job, changed the recycle buckets from bright blue to faded green, and altered the foliage colour to a more vibrant, springtime green. Done with Roy Freeware. Click any image to see a zoom-in.

Roy Shirt - Before Info

Roy Shirt - After Info

Lots of Changes

I turned the nice green grass into a yellow straw on the G channel, altered Dawn's facial colour slightly to remove the greenish cast and elevated its luminance to stand out more on the R channel, turned her bluejeans black on the B channel, changed her shirt's colour on the M channel, and fixed a little bit of yellowish skin reflection on her arm with the Y channel. Done with RoyPRO.

Roy Strawberries - Before Info

Roy Strawberries - After Info

Strawberries to Goonberries

A three channel change. Red strawberries to sickly green, green strawberry stems turned reddish, and the green box accent enhanced. Notice how Roy has altered the red radiosity of the white boxes to the same green as the goonberries. Done with Roy Freeware.

Roy Sky - Before Info

Roy Sky - After Info

Dramatic Sky

I just modified one channel in this image to make a bland sky very dramatic. Selected Blue, checked Locate, moved the centre slider till the highlight tick was in the sky, then decreased luminance and increased saturation. Total time: 10 seconds. Done with Roy Freeware.

User Interface

RoyPRO Info

Roy Freeware Info

Enable Checkbox

When checked, the plug-in can affect the image. When unchecked, disables the plug-in.

Reset Button

Resets all plug-in values to startup defaults. Useful for getting back to a sane place after experimenting wildly.

? Button

Reveal the plug-in version number, author and homepage.

Channel Tabs

Roy Freeware has three channel tabs -- Red, Green and Blue. These are just labels, however. Each channel can actually be adjusted to modify colours anywher near the channel label. The range of adjustment for each channel allows it to stretch into its adjacent channel handily, so you are not limited to just changing Red colours with the "red" channel. Red can also mean orange, yellow, magenta, skin tones, brown, beige, or any of a wide range of warm colours.

RoyPRO adds three more channels, each centred between one of Roy's -- Yellow (between red and green), Cyan (green and blue), and Magenta (blue and red). These channels overlap each other greatly, allowing you very fine control of selection and adjustment of similar colours.

Enable Checkbox

Enables this channel to affect the image. Each channel can be enabled/disabled individually.

Locate Checkbox

The locator makes it easy to adjust the correction area. Click Locate on a channel to see which parts of the image are affected by that channel. Image areas not affected at all are darkened and desaturated. Areas affected greatly show bright colour representing the channel you're working with. The selection centrepoint is shown by brighter pixels, and the feathered region of the selection is shown by areas of decreasing saturation. The locator diagram is updated in realtime as you adjust the selection sliders.

Here's some screenshots showing the locator in action. First, the normal image. Second, the green channel locator. I've centred it on the tower's copper roof. Lastly, the cyan channel locator showing the sky selected.

Huey-locator-normal Info

Roy Locator - Green Info

Roy Locator - Cyan Info

The locator turns off automatically when you change any channel adjustment sliders, or select another channel's locator.

Reset Button

Resets the current channel's selection to moderate, and alteration to nil.

Selection Control

These controls adjust the range of colour selected by this channel.

Centre Slider

To explain the centrepoint, we need to talk about how Roy thinks of hue. Roy uses the HSV colourspace. In HSV, hue is represented by a number of degrees around a circle. Red, Green and Blue are all equally spaced around the circle, separated by 120 degrees. Cyan, Magenta and Yellow also appear on the circle, each midway between (60 degrees away from) the light sources that make it up (cyan is between blue and green). Roy's channel selector uses these degrees to choose the central channel hue and to set the amount of tint change.

Each channel has a native centrepoint around the colour circle corresponding to the channel name. Adjusting the Centre slider moves the channel's centre point along the wheel, centered on the native point. The Centre slider has a range of +/- 90 degrees, allowing adjustment along fully half of the colour circle. With Roy's three channels, you have a 60 degree overlap between the channels. RoyPRO has a 120 degree overlap between each of the six channels.

Width Slider (RoyPRO)

Width is the number of adjacent colours selected in a channel in RoyPRO. In Roy freeware, this number is fixed to 80 degrees on the colour circle. RoyPRO allows you to adjust the width from 0 up to 360 degrees -- you can alter a single channel to cover the entire colour wheel (your whole image).

Soft Slider (RoyPRO)

Soft is the feathering applied to the edge of the selection. In Roy freeware, this number is fixed to 20, allowing a nice blend that works well in most retouching situations. RoyPRO allows the feathering to be adjusted from 0 for a precise hard edge to 90 degrees for a very smooth integration with the rest of the image.

Adjustment Control

These controls determine what happens to the pixels that fall within the selection area. A word, though, about "alpha." Not every pixel is selected to the same degree -- an Alpha less than 100%. Both the initial colour saturation and amount of selection feathering (if the hue is on the margin) control Alpha, which is the term for how much the adjustment controls affect the pixel's colour. Very saturated colours have a high Alpha, whereas greys and pale tones have a low Alpha. This behaviour is very important in creating a smooth retouch, but you should keep it in mind when you think that your alterations aren't actually changing much -- it is likely that the pixels you are attempting to alter pixels with a low Alpha.

Tint Slider

Tint adjusts how much the pixel's hue moves along the colour wheel. The amount of tint is determined both by the setting of this slider (+/- 180 degrees) and by Alpha. Only very saturated colours can actually be moved the entire way around the colour wheel.

Value Slider

Value adjusts the brightness of the selected image area. A value of 1.0 is not white -- it is the brightest rendition of the chosen colour. To get white in HSV, saturation must be reduced to 0. Positive adjustments of value make it brighter, negative adjustments darker. Positive value adjustments are routed through a sigmoidal function (like Siggy uses), which preserves details in highlights unless making the most extreme alterations. Negative value adjustments are simply scaled linearly downwards.

Satur. Slider

Satur., short for Saturation, adjusts the intensity of colour of the selected image area. Positive values make colours more intense, negative values make colours duller and more grey.

Notes

Black, Grey and White

Roy affects saturated colours more than unsaturated colours. Whites, blacks and greys are affected almost not at all; this allows modified areas to blend together much more attractively than if all saturation levels were affected the same.

Channel Crossover

The original pixel colour is used when selecting which channel(s) can affect that pixel. It is possible for more than one channel to affect the same pixel to some degree if the selection widths are wide enough. In these circumstances, the channel effect takes place serially in the order RYGCBM.

Note that because the original pixel hue is used for each channel selection test, not the modified pixel hue, a red pixel turned green by the red channel will NOT be selected by the subsequently evaluated green channel (unless the green channel would also select the originally red pixel by dint of having an overlapping selection).

If all this sounds confusing, just remember this: Channels do not overlap unless their selections overlap.

Colourspace

Roy uses the HSV colourspace as it provides the smoothest adjustment of saturation and value at the many

Rainbow Effects

It is possible for large (like, from red to blue) tint shifts over a range of pixels from saturated-to-unsaturated to result in an unattractive rainbow effect. The "rainbow effect" has a positive spin, though. By graduating hue adjustment with saturation, Roy is capable of correcting radiosity and reflection hues much more realistically.

Legal

References

lots.... tba

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