检查是否字符存在于编码 [英] Check if character exists in encoding
问题描述
我写的一部分呈现在CP437位图字体的程序。
在一个函数,我希望能够检查是否字符
可在CP437的编码转换之前,这样的呈现文本:
公共静态无效DrawCharacter(此图形克,焦三)
{
如果(char_exist_in_encoding(Encoding.GetEncoding(437),C){
byte []的SRC = Encoding.Uni code.GetBytes(c.ToString());
byte []的DEST = Encoding.Convert(Encoding.Uni code,Encoding.GetEncoding(437),SRC);
DrawCharacter(克,DEST [0]); //调用无效(这个图形,字节)超载
}
}
如果没有检查,CP437以外的任何字符会导致一个'?
(63 0x3F的)。我想完全隐藏任何无效字符。是否有一个执行 char_exist_in_encoding
的比下面的笨方法等的?
私有静态布尔char_exist_in_encoding(编码E,焦三)
{
如果(C =='?)
返回true;
byte []的SRC = Encoding.Uni code.GetBytes(c.ToString());
byte []的DEST = Encoding.Convert(Encoding.Uni code,E,SRC);
如果(DEST [0] == 0x3F的)
返回false;
返回true;
}
也许不是很相关,但位图这样创建的:
位图B =新位图(256 * 8,16);
图形G = Graphics.FromImage(B);
g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SingleBitPerPixelGridFit;
字体F =新的字体(不管8×16点阵字体,16,GraphicsUnit.Pixel);
对于(字节I = 0; I< 255;我++)
{
byte []的ARR = Encoding.Convert(Encoding.GetEncoding(437),Encoding.Uni code,新的byte [] {I});
焦炭C = Encoding.Uni code.GetChars(ARR)[0];
g.DrawString(c.ToString(),男,Brushes.Black,I * 8 - 3,0); //不知道为什么它需要的3px偏移
}
b.Save(@D:\ chars.png);
由于弗拉德,后恩coderFallback
我终于看到了一点研究的在MSDN 一个例子
我的工作(可能是临时的工作)code是:
公共静态无效DrawCharacter(此图形克,焦三)
{
byte []的SRC = Encoding.Uni code.GetBytes(c.ToString());
byte []的DEST = Encoding.Convert(Encoding.Uni code,Encoding.GetEncoding(437,新恩coderReplacementFallback(),新德coderReplacementFallback()),SRC);
DrawCharacter(克,DEST [0]);
}
它来代替无效字符空格,
。
PS 我原来用一个空的字符串
,
作为替代,但最后我决定使用空格字符,因为它看起来更干净。
I am writing a program that a part renders a bitmap font in CP437.
In a function that renders the text with I want to be able to check whether a char
is available in CP437 before the encoding conversion, like:
public static void DrawCharacter(this Graphics g, char c)
{
if (char_exist_in_encoding(Encoding.GetEncoding(437), c) {
byte[] src = Encoding.Unicode.GetBytes(c.ToString());
byte[] dest = Encoding.Convert(Encoding.Unicode, Encoding.GetEncoding(437), src);
DrawCharacter(g, dest[0]); // Call the void(this Graphics, byte) overload
}
}
Without the check, any characters outside CP437 will result in a '?'
(63, 0x3F). I want to hide any invalid characters completely. Is there an implementation of char_exist_in_encoding
other than the following stupid approach?
private static bool char_exist_in_encoding(Encoding e, char c)
{
if (c == '?')
return true;
byte[] src = Encoding.Unicode.GetBytes(c.ToString());
byte[] dest = Encoding.Convert(Encoding.Unicode, e, src);
if (dest[0] == 0x3F)
return false;
return true;
}
Perhaps not very relevant, but the bitmap is created like this:
Bitmap b = new Bitmap(256 * 8, 16);
Graphics g = Graphics.FromImage(b);
g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SingleBitPerPixelGridFit;
Font f = new Font("Whatever 8x16 bitmap font", 16, GraphicsUnit.Pixel);
for (byte i = 0; i < 255; i++)
{
byte[] arr = Encoding.Convert(Encoding.GetEncoding(437), Encoding.Unicode, new byte[] { i });
char c = Encoding.Unicode.GetChars(arr)[0];
g.DrawString(c.ToString(), f, Brushes.Black, i * 8 - 3, 0); // Don't know why it needs a 3px offset
}
b.Save(@"D:\chars.png");
Thanks to Vlad, after a bit research on EncoderFallback
I finally saw an example in MSDN
My working (perhaps temporary working) code is:
public static void DrawCharacter(this Graphics g, char c)
{
byte[] src = Encoding.Unicode.GetBytes(c.ToString());
byte[] dest = Encoding.Convert(Encoding.Unicode, Encoding.GetEncoding(437, new EncoderReplacementFallback(" "), new DecoderReplacementFallback(" ")), src);
DrawCharacter(g, dest[0]);
}
It replace invalid characters to a space " "
.
P.S. I originally used an empty string
""
as the replacement but finally I decided to use the space character, because it looks cleaner.
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