所以这是一个可行的解决方案。它不漂亮，速度不快（在我的笔记本电脑上是 2 秒），但输出很好。尽管我认为他们正在执行一些额外的工作，但它与 Photoshop 的输出并不完全匹配。
不同的测试图像上有时会出现轻微的莫尔条纹，但去网纹超出了当前问题的范围。
该代码执行以下步骤。
- 以给定的间隔循环遍历图像的像素
- 对于每个颜色分量，CMYK 在给定点绘制一个椭圆，该椭圆是通过将当前点旋转设定角度来计算的。这个椭圆的尺寸由每个点的每个颜色分量的级别决定。
- 通过循环像素点并在每个点添加 CMYK 颜色分量值来确定要绘制到图像的正确颜色来创建新图像。
输出图像
编码
public Image ProcessImage(ImageFactory factory)
{
Bitmap cyan = null;
Bitmap magenta = null;
Bitmap yellow = null;
Bitmap keyline = null;
Bitmap newImage = null;
Image image = factory.Image;
try
{
int width = image.Width;
int height = image.Height;
// Angles taken from Wikipedia page.
float cyanAngle = 15f;
float magentaAngle = 75f;
float yellowAngle = 0f;
float keylineAngle = 45f;
int diameter = 4;
float multiplier = 4 * (float)Math.Sqrt(2);
// Cyan color sampled from Wikipedia page.
Brush cyanBrush = new SolidBrush(Color.FromArgb(0, 153, 239));
Brush magentaBrush = Brushes.Magenta;
Brush yellowBrush = Brushes.Yellow;
Brush keylineBrush;
// Create our images.
cyan = new Bitmap(width, height);
magenta = new Bitmap(width, height);
yellow = new Bitmap(width, height);
keyline = new Bitmap(width, height);
newImage = new Bitmap(width, height);
// Ensure the correct resolution is set.
cyan.SetResolution(image.HorizontalResolution, image.VerticalResolution);
magenta.SetResolution(image.HorizontalResolution, image.VerticalResolution);
yellow.SetResolution(image.HorizontalResolution, image.VerticalResolution);
keyline.SetResolution(image.HorizontalResolution, image.VerticalResolution);
newImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);
// Check bounds against this.
Rectangle rectangle = new Rectangle(0, 0, width, height);
using (Graphics graphicsCyan = Graphics.FromImage(cyan))
using (Graphics graphicsMagenta = Graphics.FromImage(magenta))
using (Graphics graphicsYellow = Graphics.FromImage(yellow))
using (Graphics graphicsKeyline = Graphics.FromImage(keyline))
{
// Ensure cleared out.
graphicsCyan.Clear(Color.Transparent);
graphicsMagenta.Clear(Color.Transparent);
graphicsYellow.Clear(Color.Transparent);
graphicsKeyline.Clear(Color.Transparent);
// This is too slow. The graphics object can't be called within a parallel
// loop so we have to do it old school. :(
using (FastBitmap sourceBitmap = new FastBitmap(image))
{
for (int y = -height * 2; y < height * 2; y += diameter)
{
for (int x = -width * 2; x < width * 2; x += diameter)
{
Color color;
CmykColor cmykColor;
float brushWidth;
// Cyan
Point rotatedPoint = RotatePoint(new Point(x, y), new Point(0, 0), cyanAngle);
int angledX = rotatedPoint.X;
int angledY = rotatedPoint.Y;
if (rectangle.Contains(new Point(angledX, angledY)))
{
color = sourceBitmap.GetPixel(angledX, angledY);
cmykColor = color;
brushWidth = diameter * (cmykColor.C / 255f) * multiplier;
graphicsCyan.FillEllipse(cyanBrush, angledX, angledY, brushWidth, brushWidth);
}
// Magenta
rotatedPoint = RotatePoint(new Point(x, y), new Point(0, 0), magentaAngle);
angledX = rotatedPoint.X;
angledY = rotatedPoint.Y;
if (rectangle.Contains(new Point(angledX, angledY)))
{
color = sourceBitmap.GetPixel(angledX, angledY);
cmykColor = color;
brushWidth = diameter * (cmykColor.M / 255f) * multiplier;
graphicsMagenta.FillEllipse(magentaBrush, angledX, angledY, brushWidth, brushWidth);
}
// Yellow
rotatedPoint = RotatePoint(new Point(x, y), new Point(0, 0), yellowAngle);
angledX = rotatedPoint.X;
angledY = rotatedPoint.Y;
if (rectangle.Contains(new Point(angledX, angledY)))
{
color = sourceBitmap.GetPixel(angledX, angledY);
cmykColor = color;
brushWidth = diameter * (cmykColor.Y / 255f) * multiplier;
graphicsYellow.FillEllipse(yellowBrush, angledX, angledY, brushWidth, brushWidth);
}
// Keyline
rotatedPoint = RotatePoint(new Point(x, y), new Point(0, 0), keylineAngle);
angledX = rotatedPoint.X;
angledY = rotatedPoint.Y;
if (rectangle.Contains(new Point(angledX, angledY)))
{
color = sourceBitmap.GetPixel(angledX, angledY);
cmykColor = color;
brushWidth = diameter * (cmykColor.K / 255f) * multiplier;
// Just using blck is too dark.
keylineBrush = new SolidBrush(CmykColor.FromCmykColor(0, 0, 0, cmykColor.K));
graphicsKeyline.FillEllipse(keylineBrush, angledX, angledY, brushWidth, brushWidth);
}
}
}
}
// Set our white background.
using (Graphics graphics = Graphics.FromImage(newImage))
{
graphics.Clear(Color.White);
}
// Blend the colors now to mimic adaptive blending.
using (FastBitmap cyanBitmap = new FastBitmap(cyan))
using (FastBitmap magentaBitmap = new FastBitmap(magenta))
using (FastBitmap yellowBitmap = new FastBitmap(yellow))
using (FastBitmap keylineBitmap = new FastBitmap(keyline))
using (FastBitmap destinationBitmap = new FastBitmap(newImage))
{
Parallel.For(
0,
height,
y =>
{
for (int x = 0; x < width; x++)
{
// ReSharper disable AccessToDisposedClosure
Color cyanPixel = cyanBitmap.GetPixel(x, y);
Color magentaPixel = magentaBitmap.GetPixel(x, y);
Color yellowPixel = yellowBitmap.GetPixel(x, y);
Color keylinePixel = keylineBitmap.GetPixel(x, y);
CmykColor blended = cyanPixel.AddAsCmykColor(magentaPixel, yellowPixel, keylinePixel);
destinationBitmap.SetPixel(x, y, blended);
// ReSharper restore AccessToDisposedClosure
}
});
}
}
cyan.Dispose();
magenta.Dispose();
yellow.Dispose();
keyline.Dispose();
image.Dispose();
image = newImage;
}
catch (Exception ex)
{
if (cyan != null)
{
cyan.Dispose();
}
if (magenta != null)
{
magenta.Dispose();
}
if (yellow != null)
{
yellow.Dispose();
}
if (keyline != null)
{
keyline.Dispose();
}
if (newImage != null)
{
newImage.Dispose();
}
throw new ImageProcessingException("Error processing image with " + this.GetType().Name, ex);
}
return image;
}
旋转像素的附加代码如下。这可以在围绕另一个点旋转一个点中找到
为简洁起见，我省略了颜色添加代码。
/// <summary>
/// Rotates one point around another
/// <see href="https://stackoverflow.com/questions/13695317/rotate-a-point-around-another-point"/>
/// </summary>
/// <param name="pointToRotate">The point to rotate.</param>
/// <param name="centerPoint">The centre point of rotation.</param>
/// <param name="angleInDegrees">The rotation angle in degrees.</param>
/// <returns>Rotated point</returns>
private static Point RotatePoint(Point pointToRotate, Point centerPoint, double angleInDegrees)
{
double angleInRadians = angleInDegrees * (Math.PI / 180);
double cosTheta = Math.Cos(angleInRadians);
double sinTheta = Math.Sin(angleInRadians);
return new Point
{
X =
(int)
((cosTheta * (pointToRotate.X - centerPoint.X)) -
((sinTheta * (pointToRotate.Y - centerPoint.Y)) + centerPoint.X)),
Y =
(int)
((sinTheta * (pointToRotate.X - centerPoint.X)) +
((cosTheta * (pointToRotate.Y - centerPoint.Y)) + centerPoint.Y))
};
}
