学步园

Widows下只认.ico格式为程序图标，这是一种源自bmp的图片格式。ico中的颜色可以通过color table来表示也可以直接通过RGBA数组表示。

ico文件的格式见官方文档：

http://msdn.microsoft.com/en-us/library/ms997538.aspx

http://msdn.microsoft.com/en-us/library/windows/desktop/dd183376%28v=vs.85%29.aspx

其它一些关于ico文件的文档见：

比较详细的原理介绍：http://blogs.msdn.com/b/oldnewthing/archive/2010/10/18/10077133.aspx

ico格式描述：http://www.daubnet.com/en/file-format-ico

Programming Tips & Tricks：http://tipsandtricks.runicsoft.com/Cpp/BitmapTutorial.html

bmp和ico格式描述：http://www.digicamsoft.com/bmp/bmp.html

ico文件相关实现：

IconImagePlugin in Python PIL: http://code.google.com/p/casadebender/source/browse/python/PIL/Win32IconImagePlugin.py

construct ico from RGBA array - a python implementation：http://fayaa.com/code/view/6094/

png2ico：http://www.winterdrache.de/freeware/png2ico/

下面是一个用从RGBA生成ico文件的C语言实现，生成一个红色的图标文件 - test.ico。

#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>

void Fwrite(FILE * f, char * data, int byte)
{
	if (1 != fwrite(data, byte, 1, f)) {
		perror("fwrite error");
		exit(1);
	}
}

void WriteByte(FILE* f, unsigned int val, int byte)
{
    char data[4];
    assert(byte <= 4);
    memcpy((void *)data, (void *)&val, byte);
    Fwrite(f, data, byte);
};


void generate_ico_file(const char * filename, char * body, 
        int width, int height, int has_alpha)
{
    int x, y;
    int index = 0;
    int Size = 0;
    int offset= 6 + 1 * 16;
    int bpp = 32;

    FILE* outfile=fopen(filename,"wb");
    if (outfile==NULL) {
        perror("fopen error"); 
        exit(1);
    };

    WriteByte(outfile,0, 2);				//idReserved
    WriteByte(outfile,1, 2);				//idType
    WriteByte(outfile,1, 2);				//idCount 

    WriteByte(outfile,width, 1);			//bWidth
    WriteByte(outfile,height, 1);			//bHeight
    WriteByte(outfile,0, 1);				//bColorCount
    WriteByte(outfile,0, 1);				//bReserved
    WriteByte(outfile,1, 2);				//wPlanes
    WriteByte(outfile,bpp, 2);				//wBitCount
    Size = 40 + height * ((width + 31) / 32 * 32 / 8 + width * 3);	//Note 4 bytes alignment
    if (bpp == 32)
        Size += height * width;
    WriteByte(outfile,Size, 4);			//dwBytesInRes
    WriteByte(outfile,offset, 4);			//dwImageOffset

    WriteByte(outfile,40, 4);				//biSize
    WriteByte(outfile,width, 4);			//biWidth
    WriteByte(outfile,2 * height, 4);		//biHeight 
    WriteByte(outfile,1, 2);				//biPlanes
    WriteByte(outfile,bpp, 2);				//biBitCount
    WriteByte(outfile,0, 4);				//biCompression
    WriteByte(outfile,0, 4);				//biSizeImage
    WriteByte(outfile,0, 4);				//biXPelsPerMeter   
    WriteByte(outfile,0, 4);				//biYPelsPerMeter
    WriteByte(outfile,0, 4);				//biClrUsed 
    WriteByte(outfile,0, 4);				//biClrImportant

    // XOR mask
    for (y= height - 1; y >= 0; --y) { 
        for (x = 0; x < width; ++x) {
            index = (y * width + x) * 4;
            WriteByte(outfile, body[index], 1);        //Blue 
            WriteByte(outfile, body[index + 1], 1);    //Green
            WriteByte(outfile, body[index + 2], 1);    //Red
            WriteByte(outfile, has_alpha ? body[index + 3] : 255, 1); //Alpha
        }
    }

    // AND mask
    for (y = 0; y < (height * ((width + 31) / 32 * 32 / 8)); ++y) { 
        WriteByte(outfile, 0, 1);
    }

    fclose(outfile);
}

#define WIDTH   72
#define HEIGHT  72

int main()
{
    int image[WIDTH * HEIGHT];
    int i, j;
    for (i = 0; i < HEIGHT; ++i) {
        for (j = 0; j < WIDTH; ++j) {
           image[i * WIDTH + j]  = 0xFFFF0000;  	// pure red icon, for test
        }
    }

    generate_ico_file("test.ico", (char *)image, WIDTH, HEIGHT, 1);

    return 0;
}