如何:縮放期間使用插補法模式控制影像品質
物件的插補模式 Graphics 會影響 GDI+ 縮放(縮放和縮小)影像的方式。 列舉 InterpolationMode 會定義數種插補模式,其中一些會在下列清單中顯示:
若要延展影像,原始影像中的每個像素都必須對應至較大影像中的圖元群組。 若要壓縮影像,原始影像中的圖元群組必須對應至較小的影像中的單一圖元。 執行這些對應之演算法的有效性會決定縮放影像的品質。 產生高品質縮放影像的演算法往往需要更多的處理時間。 在上述清單中, NearestNeighbor 是最低品質模式,而且 HighQualityBicubic 是最高品質模式。
若要設定插補模式,請將 列舉的 InterpolationMode 其中一個成員指派給 InterpolationMode 對象的屬性 Graphics 。
範例
下列範例會繪製影像,然後使用三種不同的插補模式壓縮影像。
下圖顯示原始影像和三個較小的影像。
Image image = new Bitmap("GrapeBunch.bmp");
int width = image.Width;
int height = image.Height;
// Draw the image with no shrinking or stretching.
e.Graphics.DrawImage(
image,
new Rectangle(10, 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,
null);
// Shrink the image using low-quality interpolation.
e.Graphics.InterpolationMode = InterpolationMode.NearestNeighbor;
e.Graphics.DrawImage(
image,
new Rectangle(10, 250, (int)(0.6 * width), (int)(0.6 * height)),
// destination rectangle
0,
0, // upper-left corner of source rectangle
width, // width of source rectangle
height, // height of source rectangle
GraphicsUnit.Pixel);
// Shrink the image using medium-quality interpolation.
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBilinear;
e.Graphics.DrawImage(
image,
new Rectangle(150, 250, (int)(0.6 * width), (int)(0.6 * height)),
// destination rectangle
0,
0, // upper-left corner of source rectangle
width, // width of source rectangle
height, // height of source rectangle
GraphicsUnit.Pixel);
// Shrink the image using high-quality interpolation.
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
e.Graphics.DrawImage(
image,
new Rectangle(290, 250, (int)(0.6 * width), (int)(0.6 * height)),
// destination rectangle
0,
0, // upper-left corner of source rectangle
width, // width of source rectangle
height, // height of source rectangle
GraphicsUnit.Pixel);
Dim image As New Bitmap("GrapeBunch.bmp")
Dim width As Integer = image.Width
Dim height As Integer = image.Height
' Draw the image with no shrinking or stretching. 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(10, 10, width, height), _
0, _
0, _
width, _
height, _
GraphicsUnit.Pixel, _
Nothing)
' Shrink the image using low-quality interpolation.
e.Graphics.InterpolationMode = InterpolationMode.NearestNeighbor
' Pass in the destination rectangle, and the upper-left corner, width,
' and height of the source rectangle as above.
e.Graphics.DrawImage( _
image, _
New Rectangle(10, 250, CInt(0.6 * width), CInt(0.6 * height)), _
0, _
0, _
width, _
height, _
GraphicsUnit.Pixel)
' Shrink the image using medium-quality interpolation.
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBilinear
' Pass in the destination rectangle, and the upper-left corner, width,
' and height of the source rectangle as above.
e.Graphics.DrawImage( _
image, _
New Rectangle(150, 250, CInt(0.6 * width), _
CInt(0.6 * height)), _
0, _
0, _
width, _
height, _
GraphicsUnit.Pixel)
' Shrink the image using high-quality interpolation.
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic
' Pass in the destination rectangle, and the upper-left corner, width,
' and height of the source rectangle as above.
e.Graphics.DrawImage( _
image, _
New Rectangle(290, 250, CInt(0.6 * width), CInt(0.6 * height)), _
0, _
0, _
width, _
height, _
GraphicsUnit.Pixel)
編譯程式碼
上述範例是專為搭配 Windows Forms 使用而設計,而且需要 PaintEventArgs e
,這是事件處理程式的參數 Paint 。