RGB格式等比例缩放

原理为：将原始图像的每个像素通过一个比例关系式映射到相应的位置。

/*

 lrgb:   input 24bits rgb buffer

 srgb:   output 24bits rgb buffer

 width:  input width

 height: input height

 xscale: changed vector

 yscale: changed vector

 */

int lrgbtosrgb(unsigned char *lrgb, unsigned char *srgb, int width, int height, float xscale, float yscale)

{

        int in = 0, out = 0;

        int ox, oy;     //the pixel site is after changed

        int rx, ry;     //the pixel site is before changed

        int temp = 0;   //turn site(x,y) to memory storage

        int outwidth = width * xscale;      //after changed width

        int outheight = height * yscale;    //after changed height

        //rx = ox/xscale + 0.5;     // out--to--input

        //ry = oy/yscale + 0.5;     // out--to--input

        for(oy = 0; oy < outheight; oy++)

        {

                ry = (int)(oy/0.5 + 0.5);

                if(ry >= height)

                        ry--;

                temp = ry * width *3;   //origion pixel site of which width

                for(ox = 0; ox < outwidth; ox++)

                {

                        rx = (int)(ox/0.5 + 0.5);

                        if(rx >= width)

                                rx--;

                        in = temp + rx * 3;     //change site(x,y) to storage

                        srgb[out+0] = lrgb[in+0];

                        srgb[out+1] = lrgb[in+1];

                        srgb[out+2] = lrgb[in+2];

                        out += 3;

                }

        }

        return 0;

}