CIELAB颜色空间中的坐标范围是多少? [英] What are the ranges of coordinates in the CIELAB color space?
问题描述
我有以下代码:
public List< Tuple< double,double ,double>> GetNormalizedPixels(位图图像)
{
System.Drawing.Imaging.BitmapData数据= image.LockBits(
new Rectangle(0,0,image.Width,image.Height),
System.Drawing.Imaging.ImageLockMode.ReadOnly,
image.PixelFormat);
int pixelSize = Image.GetPixelFormatSize(image.PixelFormat)/ 8;
var result = new List< Tuple< double,double,double>>();
不安全
{
for(int y = 0; y {
byte * row =( byte *)data.Scan0 +(y * data.Stride);
for(int x = 0; x< data.Width; ++ x)
{
Color c = Color.FromArgb(
row [x * pixelSize + 3],
row [x * pixelSize + 2],
row [x * pixelSize + 1],
row [x * pixelSize]);
//(*)
结果.Add(Tuple.Create(
1.0 * cR / 255,
1.0 * cG / 255,
1.0 * cB / 255);
}
}
}
image.UnlockBits(data);
返回结果;
}
关键片段(*)是这样的:
result.Add(Tuple.Create(
1.0 * cR / 255,
1.0 * cG / 255,
1.0 * cB / 255);
会添加一个像素,其像素缩放到范围 [0,1]
可以进一步用于具有不同分类器的分类任务中,其中一些需要像这样对属性进行规范化,而另一些则不在乎-因此此功能。
但是,当我想对不同于 RGB
的颜色空间中的像素进行分类时,我该怎么办,例如 L * a * b *
? RGB
颜色空间中所有坐标的ile值在 L *中的范围
颜色空间 [0,256)
据说a * b * a *
和 b *
是无界的。
因此,当将片段(*)更改为:
Lab lab = c.ToLab();
结果。Add(Tuple.Create(
1.0 * lab.L / 100,
1.0 * lab.A /?,
1.0 * lab.B / ?);
( ToLab
是扩展名方法,使用此处)中的适当算法实现。
我该问些什么?
实际上所有 RGB的数量
颜色是有限的,因此 L * a * b *
的空间是有界的,可以使用以下简单程序轻松找到坐标范围:
颜色c;
double maxL = double.MinValue;
double maxA = double.MinValue;
double maxB = double.MinValue;
double minL = double.MaxValue;
double minA = double.MaxValue;
double minB = double.MaxValue ;(int r = 0; r <256; ++ r)的
(int g = 0; g <256; ++ g)
(int b = 0; b< 256; ++ b)
{
c = Color.FromArgb(r,g,b);
Lab lab = c.ToLab();
maxL = Math.Max(maxL,lab.L);
maxA = Math.Max(maxA,lab.A);
maxB = Math.Max(maxB,lab.B);
minL = Math.Min(minL,lab.L);
minA = Math.Min(minA,lab.A);
minB = Math.Min(minB,lab.B);
}
Console.WriteLine( maxL =" + maxL +",maxA =" + maxA +",maxB =" + maxB);
Console.WriteLine( minL = + minL +,minA = + minA +,minB = + minB);
或使用任何其他语言的类似语言。
因此, CIELAB
空间坐标范围如下:
[0,100]中的L
[-86.185,98.254]中的A $ p $ b
[-107.863,94.482]中的b
B
答案是:
Lab lab = c.ToLab();
结果。Add(Tuple.Create(
1.0 * lab.L / 100,
1.0 *(lab.A + 86.185)/ 184.439,
1.0 * (实验室B + 107.863)/ 202.345);
I have the following piece of code:
public List<Tuple<double, double, double>> GetNormalizedPixels(Bitmap image)
{
System.Drawing.Imaging.BitmapData data = image.LockBits(
new Rectangle(0, 0, image.Width, image.Height),
System.Drawing.Imaging.ImageLockMode.ReadOnly,
image.PixelFormat);
int pixelSize = Image.GetPixelFormatSize(image.PixelFormat) / 8;
var result = new List<Tuple<double, double, double>>();
unsafe
{
for (int y = 0; y < data.Height; ++y)
{
byte* row = (byte*)data.Scan0 + (y * data.Stride);
for (int x = 0; x < data.Width; ++x)
{
Color c = Color.FromArgb(
row[x * pixelSize + 3],
row[x * pixelSize + 2],
row[x * pixelSize + 1],
row[x * pixelSize]);
// (*)
result.Add(Tuple.Create(
1.0 * c.R / 255,
1.0 * c.G / 255,
1.0 * c.B / 255);
}
}
}
image.UnlockBits(data);
return result;
}
The key fragment (*) is this:
result.Add(Tuple.Create(
1.0 * c.R / 255,
1.0 * c.G / 255,
1.0 * c.B / 255);
which adds a pixel with its components scaled to range [0, 1]
to be further used in classification tasks with different classifiers. Some of them require the attributes to be normalized like this, others don't care - hence this function.
However, what should I do when I'd like to classify pixels in a different colour space than RGB
, like L*a*b*
? While values of all coordinates in RGB
colour space fall into range [0,256)
in L*a*b*
colour space a*
and b*
are said to be unbounded.
So when changing the fragment (*) to:
Lab lab = c.ToLab();
result.Add(Tuple.Create(
1.0 * lab.L / 100,
1.0 * lab.A / ?,
1.0 * lab.B / ?);
(ToLab
is an extension method, implemented using appropriate algorithms from here)
what should I put for the question marks?
In practice the number of all possible RGB
colours is finite, so the L*a*b*
space is bounded. It is easy to find the ranges of coordinates with the following simple program:
Color c;
double maxL = double.MinValue;
double maxA = double.MinValue;
double maxB = double.MinValue;
double minL = double.MaxValue;
double minA = double.MaxValue;
double minB = double.MaxValue;
for (int r = 0; r < 256; ++r)
for (int g = 0; g < 256; ++g)
for (int b = 0; b < 256; ++b)
{
c = Color.FromArgb(r, g, b);
Lab lab = c.ToLab();
maxL = Math.Max(maxL, lab.L);
maxA = Math.Max(maxA, lab.A);
maxB = Math.Max(maxB, lab.B);
minL = Math.Min(minL, lab.L);
minA = Math.Min(minA, lab.A);
minB = Math.Min(minB, lab.B);
}
Console.WriteLine("maxL = " + maxL + ", maxA = " + maxA + ", maxB = " + maxB);
Console.WriteLine("minL = " + minL + ", minA = " + minA + ", minB = " + minB);
or a similar one using any other language.
So, CIELAB
space coordinate ranges are as follows:
L in [0, 100]
A in [-86.185, 98.254]
B in [-107.863, 94.482]
and the answer is:
Lab lab = c.ToLab();
result.Add(Tuple.Create(
1.0 * lab.L / 100,
1.0 * (lab.A + 86.185) / 184.439,
1.0 * (lab.B + 107.863) / 202.345);
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