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Not coming from a graphics based background my method may not be the best solution, but it seems to work just fine.

To apply a color wash a base RGB color value is decided upon as a reference point and an adjustment value calculated for the color wash’s RGB value to be applied. This adjustment is calculated for each of the red, green and blue components. Once this is done each of the image’s pixel’s red, green and blue components is adjusted by the calculated amount to produce the color wash.

Each of the RGB components of a color can be represented by values from 0 to 255, so taking the mid point of 127 as the base reference point and taking the desired RGB component values of the color wash to apply we can calculate the adjustments to be made to each pixel.

Adjusting red, green and blue component values can sometimes result in a value outside the allowed range of 0 to 255; in these cases we compromise and simply use the minimum or maximum value allowed as appropriate.

The table below illustrates how values are adjusted:

	Hex Value	Red	Green	Blue	Color
Base Color	7F7F7F	127	127	127
Color Wash To Apply	1280AA	18	128	170
Adjustment Value To Use		18 – 127 = -109	128 – 127 = 1	170 – 127 = 43
Example Pixel 1 Original Color	A5A5A5	165	165	165
Example Pixel 1 Washed Color	38A6D0	165 – 109 = 56	165 + 1 = 166	165 + 43 = 208
Example Pixel 2 Original Color	545454	84	84	84
Example Pixel 2 Washed Color	00557F	84 – 109 = -25 = 0 *	84 + 1 = 85	84 + 43 = 127
Example Pixel 3 Original Color	2E2E2E	46	46	46
Example Pixel 3 Washed Color	002F59	46 – 109 = -63 = 0 *	46 + 1 = 47	46 + 43 = 89

* The value is less than the minimum allowed so we use the minimum instead.

Using the Code

To use this functionality in your projects simply download the source files accompanying this article, drop GavDev.Image.dll into the bin directory of your project then make a reference to the class library GavDev.Image.dll. There’s two interfaces provided for your convenience:

The first interface accepts individual red, green and blue values:

ColorWashImage(ByVal FilePathOriginal As String,ByVal FilePathNew As String,ByVal Red As Integer,ByVal Green As Integer,ByVal Blue As Integer,Optional ByVal Quality As Integer = 100,Optional ByVal Encoding As String = "image/jpeg")

The second interface allows you to pass a single combined 6 digit hexadecimal RGB value in as the color wash value:

ColorWashImage(ByVal FilePathOriginal As String,ByVal FilePathNew As String,ByVal HexRGBValue As String,Optional ByVal Quality As Integer = 100,Optional ByVal Encoding As String = "image/jpeg")

Both interfaces expect parameters FilePathOriginal, the physical location of the original grayscale image and FilePathNew, the physical location to save the resulting color washed image. Optional parameters are also present to dictate the quality and encoding of the output images.

Below is an example of the class being used as it is in the accompanying demo project:

GavDev.Image.Manipulate.ColorWashImage(Server.MapPath("Images/Gav.jpg"),Server.MapPath("Images/Gav." & txtColorWash.Text & ".jpg"),txtColorWash.Text)