縮放色彩

發行項
04/11/2008

縮放變換會將四個色彩元素中的一或多個乘以一個數字。代表縮放的色彩矩陣項目列在下列表格中。

要縮放的元素	矩陣項目
紅色	[0][0]
綠色	[1][1]
藍色	[2][2]
Alpha	[3][3]

下列範例會從 ColorBars2.bmp 檔案建構 Image 物件，然後程式碼會以因數 2 縮放影像中每一個像素的藍色元素。原始影像就繪製在變換影像的旁邊。

Dim image = 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)
[C#]
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);

下圖左邊顯示的是原始的影像，右邊顯示的是縮放的影像。

下列表格會列出藍色縮放前後四列的色彩向量。請注意，四列色彩中的藍色元素是從 0.8 到 0.6。這是因為 GDI+ 只會保留結果的小數部份。例如，(2)(0.8) = 1.6，1.6 的小數部份就是 0.6。只保留小數部份可確保結果一定會在 [0, 1] 之間。

原始的	縮放的
(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)

下列範例會從 ColorBars2.bmp 檔案建構 Image 物件，然後程式碼會縮放影像中每一個像素的紅色、綠色和藍色元素。紅色元素會縮小 25%，綠色元素會縮小 35%，藍色元素會縮小 50%。

Dim image = 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)
[C#]
Image image = new Bitmap("ColorBars.bmp");
ImageAttributes imageAttributes = new ImageAttributes();
int width = image.Width;
int height = image.Height;

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

下圖左邊顯示的是原始的影像，右邊顯示的是縮放的影像。

下列表格會列出紅色、綠色和藍色縮放前後四列的色彩向量。

原始的	縮放的
(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)

共用方式為

縮放色彩

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