在的WinForms的DrawImage（）函数无法正常工作 [英] DrawImage() function over WinForms does not work correctly

问题描述

我已经创建了一个位图1个像素宽和放大器; 256像素的高度，当我尝试画这个图作为2个像素宽的使用：

 公共无效的DrawImage（图片形象，的RectangleF矩形） 
  

位图是不正确绘制，因为有每个位图列的白色条纹渺茫。
见下文

 私人无效Form1_Paint（对象发件人，PaintEventArgs的E）
 {$ B的简单代码$ b图形克= e.Graphics; 
 
位图位图=新位图（1，256）; 
为（INT Y = 0; Y< 256; Y ++）
 {
 bitmap.SetPixel（0，Y，Color.Red）; 
} 
 
的RectangleF rectf =新的RectangleF（）; 
的for（int x = 0; X< 500; X ++）
 {
浮动系数= 2; 
 rectf.X = X *因素; 
 rectf.Y = 0; 
 rectf.Width =事实; 
 rectf.Height = 500; 
 //应该吸取位图作为2个像素宽，但在每一个位图colomn 
 gr.DrawImage（位图，rectf）之间有白色条纹纤细绘制它; 
} 
} 
  

解决方案

这是Graphics.InterpolationMode的副作用，位图缩放产生伪像，当它在中位图的边缘耗尽像素。而且有很多用位图，这只是一个像素宽耗尽像素的。你可以将其设置为最近邻，并通过设置PixelOffsetMode为None取得更好的成绩。这仍然是它的外观产生伪影，虽然，一些内部舍入误差。不知道，我在的事实的价值猜测。

避免结垢小位图。

i've created a BitMap 1 pixel wide & 256 pixel height when i try to draw this bitmap as 2 pixels wide using:

public void DrawImage(Image image,RectangleF rect)

the bitmap is not drawn correctly because there are white slim stripes between each bitmap column. see the simple code below

private void Form1_Paint(object sender, PaintEventArgs e)
{
    Graphics gr = e.Graphics;

    Bitmap bitmap = new Bitmap(1, 256);
    for (int y = 0; y < 256; y++)
    {
        bitmap.SetPixel(0, y, Color.Red);
    }

    RectangleF rectf = new RectangleF();
    for (int x = 0; x < 500; x++)
    {
        float factor = 2;
        rectf.X = x*factor;
        rectf.Y = 0;
        rectf.Width = fact;
        rectf.Height = 500;
        // should draw bitmap as 2 pixels wide but draws it with white slim stripes in between each bitmap colomn
        gr.DrawImage(bitmap, rectf);
    }           
}

解决方案

This is a side effect of Graphics.InterpolationMode, bitmap scaling produces artifacts when it runs out of pixels at the edge of the bitmap. And there's a lot of running out of pixels with a bitmap that's only one pixel wide. You can get better results by setting it to NearestNeighbor and by setting PixelOffsetMode to None. This still produces artifacts though, some internal round-off error by the looks of it. Not sure, I had to guess at the value of "fact".

Avoid scaling small bitmaps.

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