public static TextColor GetBestTextColor(TextColor fgColor,
TextColor bgColor,
TextColorContrast neededContrast)
{
if (fgColor == null) {
throw new ArgumentNullException("fgColor");
}
if (bgColor == null) {
throw new ArgumentNullException("bgColor");
}
TextColor bestColor;
int key = fgColor.Value ^ bgColor.Value ^ (int) neededContrast;
if (f_BestContrastColors.TryGetValue(key, out bestColor)) {
return bestColor;
}
double brDiff = GetBritnessDifference(bgColor, TextColor.White);
int modifier = 0;
// for bright backgrounds we need to go from bright to dark colors
// for better contrast and for dark backgrounds the opposite
if (brDiff < 127) {
// bright background
modifier = -10;
} else {
// dark background
modifier = 10;
}
double lastDifference = 0;
bestColor = fgColor;
int attempts = 1;
while (true) {
double difference = GetLuminanceDifference(bestColor, bgColor);
double needed = ((int) neededContrast) / 10d;
if (difference > needed) {
break;
}
#if LOG4NET && COLOR_DEBUG
f_Logger.Debug("GetBestTextColor(): color has bad contrast: " +
bestColor + " difference: " + difference +
" needed: " + needed);
#endif
// change the fg color
int red = bestColor.Red + modifier;
int green = bestColor.Green + modifier;
int blue = bestColor.Blue + modifier;
// cap to allowed values
if (modifier > 0) {
if (red > 255) {
red = 255;
}
if (green > 255) {
green = 255;
}
if (blue > 255) {
blue = 255;
}
} else {
if (red < 0) {
red = 0;
}
if (green < 0) {
green = 0;
}
if (blue < 0) {
blue = 0;
}
}
bestColor = new TextColor((byte) red, (byte) green, (byte) blue);
// in case we found no good color
if (bestColor == TextColor.White ||
bestColor == TextColor.Black) {
break;
}
attempts++;
}
#if LOG4NET && COLOR_DEBUG
f_Logger.Debug(
String.Format(
"GetBestTextColor(): found good contrast: {0}|{1}={2} " +
"({3}) attempts: {4}", fgColor, bgColor, bestColor,
neededContrast, attempts
)
);
#endif
f_BestContrastColors.Add(key, bestColor);
return bestColor;
}
public static TextColor GetBestTextColor(TextColor fgColor,
TextColor bgColor,
TextColorContrast neededContrast)
{
if (fgColor == null)
{
throw new ArgumentNullException("fgColor");
}
if (bgColor == null)
{
throw new ArgumentNullException("bgColor");
}
TextColor bestColor;
int key = fgColor.Value ^ bgColor.Value ^ (int)neededContrast;
if (f_BestContrastColors.TryGetValue(key, out bestColor))
{
return(bestColor);
}
double brDiff = GetBritnessDifference(bgColor, TextColor.White);
int modifier = 0;
// for bright backgrounds we need to go from bright to dark colors
// for better contrast and for dark backgrounds the opposite
if (brDiff < 127)
{
// bright background
modifier = -10;
}
else
{
// dark background
modifier = 10;
}
double lastDifference = 0;
bestColor = fgColor;
int attempts = 1;
while (true)
{
double difference = GetLuminanceDifference(bestColor, bgColor);
double needed = ((int)neededContrast) / 10d;
if (difference > needed)
{
break;
}
#if LOG4NET && COLOR_DEBUG
f_Logger.Debug("GetBestTextColor(): color has bad contrast: " +
bestColor + " difference: " + difference +
" needed: " + needed);
#endif
// change the fg color
int red = bestColor.Red + modifier;
int green = bestColor.Green + modifier;
int blue = bestColor.Blue + modifier;
// cap to allowed values
if (modifier > 0)
{
if (red > 255)
{
red = 255;
}
if (green > 255)
{
green = 255;
}
if (blue > 255)
{
blue = 255;
}
}
else
{
if (red < 0)
{
red = 0;
}
if (green < 0)
{
green = 0;
}
if (blue < 0)
{
blue = 0;
}
}
bestColor = new TextColor((byte)red, (byte)green, (byte)blue);
// in case we found no good color
if (bestColor == TextColor.White ||
bestColor == TextColor.Black)
{
break;
}
attempts++;
}
#if LOG4NET && COLOR_DEBUG
f_Logger.Debug(
String.Format(
"GetBestTextColor(): found good contrast: {0}|{1}={2} " +
"({3}) attempts: {4}", fgColor, bgColor, bestColor,
neededContrast, attempts
)
);
#endif
f_BestContrastColors.Add(key, bestColor);
return(bestColor);
}