使用转换来调整颜色

  • 项目

缩放转换将四个颜色分量中的一个或多个分量乘以一个数字。 下表提供了表示缩放的颜色矩阵条目。

要缩放的分量 矩阵条目
红色 [0][0]
绿色 [1][1]
蓝色 [2][2]
Alpha [3][3]

缩放一种颜色

以下示例从 ColorBars2.bmp 文件构造 Image 对象。 然后，代码将图像中每个像素的蓝色分量缩放 2 倍。 原始图像绘制在转换后的图像旁边。

Image image = new Bitmap("ColorBars2.bmp");
ImageAttributes imageAttributes = new ImageAttributes();
int width = image.Width;
int height = image.Height;

float[][] colorMatrixElements = {
   new float[] {1,  0,  0,  0, 0},
   new float[] {0,  1,  0,  0, 0},
   new float[] {0,  0,  2,  0, 0},
   new float[] {0,  0,  0,  1, 0},
   new float[] {0, 0, 0, 0, 1}};

ColorMatrix colorMatrix = new ColorMatrix(colorMatrixElements);

imageAttributes.SetColorMatrix(
   colorMatrix,
   ColorMatrixFlag.Default,
   ColorAdjustType.Bitmap);

e.Graphics.DrawImage(image, 10, 10, width, height);

e.Graphics.DrawImage(
   image,
   new Rectangle(150, 10, width, height),  // destination rectangle
   0, 0,        // upper-left corner of source rectangle
   width,       // width of source rectangle
   height,      // height of source rectangle
   GraphicsUnit.Pixel,
   imageAttributes);

Dim image As New Bitmap("ColorBars2.bmp")
Dim imageAttributes As New ImageAttributes()
Dim width As Integer = image.Width
Dim height As Integer = image.Height

Dim colorMatrixElements As Single()() = { _
   New Single() {1, 0, 0, 0, 0}, _
   New Single() {0, 1, 0, 0, 0}, _
   New Single() {0, 0, 2, 0, 0}, _
   New Single() {0, 0, 0, 1, 0}, _
   New Single() {0, 0, 0, 0, 1}}

Dim colorMatrix As New ColorMatrix(colorMatrixElements)

imageAttributes.SetColorMatrix( _
   colorMatrix, _
   ColorMatrixFlag.Default, _
   ColorAdjustType.Bitmap)

e.Graphics.DrawImage(image, 10, 10, width, height)

' Pass in the destination rectangle (2nd argument), the upper-left corner 
' (3rd and 4th arguments), width (5th argument),  and height (6th 
' argument) of the source rectangle.
e.Graphics.DrawImage( _
   image, _
   New Rectangle(150, 10, width, height), _
   0, 0, _
   width, _
   height, _
   GraphicsUnit.Pixel, _
   imageAttributes)

下图左侧显示原始图像，右侧显示缩放后的图像：

Screenshot that compares the original and scaled colors.

下表列出了蓝色缩放前后四条色带的颜色矢量。 请注意，第四条色带的蓝色分量从 0.8 变为 0.6。 这是因为 GDI+ 只保留结果的小数部分。 例如，(2)(0.8) = 1.6，1.6 的小数部分为 0.6。 仅保留小数部分可确保结果始终处于 [0, 1] 区间内。

原始 缩放后
(0.4, 0.4, 0.4, 1) (0.4, 0.4, 0.8, 1)
(0.4, 0.2, 0.2, 1) (0.4, 0.2, 0.4, 1)
(0.2, 0.4, 0.2, 1) (0.2, 0.4, 0.4, 1)
(0.4, 0.4, 0.8, 1) (0.4, 0.4, 0.6, 1)

缩放多个颜色

以下示例从 ColorBars2.bmp 文件构造 Image 对象。 然后，代码缩放图像中每个像素的红色、绿色和蓝色分量。 红色分量缩小 25%，绿色分量缩小 35%，蓝色组件分量缩小 50%。

Image image = new Bitmap("ColorBars.bmp");
ImageAttributes imageAttributes = new ImageAttributes();
int width = image.Width;
int height = image.Height;

float[][] colorMatrixElements = {
   new float[] {.75F,  0,  0,  0, 0},
   new float[] {0,  .65F,  0,  0, 0},
   new float[] {0,  0,  .5F,  0, 0},
   new float[] {0,  0,  0,  1F, 0},
   new float[] {0, 0, 0, 0, 1F}};

ColorMatrix colorMatrix = new ColorMatrix(colorMatrixElements);

imageAttributes.SetColorMatrix(
   colorMatrix,
   ColorMatrixFlag.Default,
   ColorAdjustType.Bitmap);

e.Graphics.DrawImage(image, 10, 10, width, height);

e.Graphics.DrawImage(
   image,
   new Rectangle(150, 10, width, height),  // destination rectangle
   0, 0,        // upper-left corner of source rectangle
   width,       // width of source rectangle
   height,      // height of source rectangle
   GraphicsUnit.Pixel,
   imageAttributes);

Dim image As New Bitmap("ColorBars.bmp")
Dim imageAttributes As New ImageAttributes()
Dim width As Integer = image.Width
Dim height As Integer = image.Height

Dim colorMatrixElements As Single()() = { _
   New Single() {0.75F, 0, 0, 0, 0}, _
   New Single() {0, 0.65F, 0, 0, 0}, _
   New Single() {0, 0, 0.5F, 0, 0}, _
   New Single() {0, 0, 0, 1, 0}, _
   New Single() {0, 0, 0, 0, 1}}

Dim colorMatrix As New ColorMatrix(colorMatrixElements)

imageAttributes.SetColorMatrix( _
   colorMatrix, _
   ColorMatrixFlag.Default, _
   ColorAdjustType.Bitmap)

e.Graphics.DrawImage(image, 10, 10, width, height)

' Pass in the destination rectangle, and the upper-left corner, width, 
' and height of the source rectangle as in the previous example.
e.Graphics.DrawImage( _
   image, _
   New Rectangle(150, 10, width, height), _
   0, 0, _
   width, _
   height, _
   GraphicsUnit.Pixel, _
   imageAttributes)

下图左侧显示原始图像，右侧显示缩放后的图像：

Screenshot that compares the original and scaled red, green, and blue components.

下表列出了红色、绿色和蓝色缩放前后四条色带的颜色矢量。

原始 缩放后
(0.6, 0.6, 0.6, 1) (0.45, 0.39, 0.3, 1)
(0, 1, 1, 1) (0, 0.65, 0.5, 1)
(1, 1, 0, 1) (0.75, 0.65, 0, 1)
(1, 0, 1, 1) (0.75, 0, 0.5, 1)

另请参阅