EasyX圖形庫，繪制透明和旋轉圖片的方法（效率很高）

#ifndef EX_EASYX_H
#define EX_EASYX_H

#include <graphics.h>

#define _USE_MATH_DEFINES
#include <math.h>

#ifndef M_RD
#define M_RD 0.01745329251994329576923690768489
#endif

//2x3矩陣
class gdimat2 : public XFORM
{
public:
	gdimat2()
	{
		this->identity();
	}

	void identity()
	{
		eM11 = 1.0f; eM12 = 0.0f;
		eM21 = 0.0f; eM22 = 1.0f;
		eDx = 0.0f; eDy = 0.0f;
	}

	void translate(float x, float y)
	{
		XFORM mat;
		mat.eM11 = 1.0f; mat.eM12 = 0.0f;
		mat.eM21 = 0.0f; mat.eM22 = 1.0f;
		mat.eDx = x;
		mat.eDy = y;
		CombineTransform(this, this, &mat);
	}

	void scale(float x, float y)
	{
		XFORM mat;
		mat.eM11 = x;    mat.eM12 = 0.0f;
		mat.eM21 = 0.0f; mat.eM22 = y;
		mat.eDx = 0.0f;
		mat.eDy = 0.0f;
		CombineTransform(this, this, &mat);
	}

	void rotate(float angle)
	{
		using namespace std;
		XFORM mat;
		angle *= M_RD;
		float cosin = cos(angle);
		float sine = sin(angle);
		mat.eM11 = cosin; mat.eM12 = sine;
		mat.eM21 = -sine; mat.eM22 = cosin;
		mat.eDx = 0.0f;
		mat.eDy = 0.0f;
		CombineTransform(this, this, &mat);
	}

	//應用到目標HDC
	void use(HDC dc)
	{
		SetWorldTransform(dc, this);
	}
};

//easyx擴展，繪制透明png圖片
#pragma comment (lib, "MSIMG32.lib")
void draw_image(IMAGE& image, int x, int y, int w = -1, int h = -1)
{
	BLENDFUNCTION blendfunc = { AC_SRC_OVER, 0, 255, AC_SRC_ALPHA };
	int width = image.getwidth();
	int height = image.getheight();
	if (w == -1)w = width;
	if (h == -1)h = height;
	AlphaBlend(GetImageHDC(), x, y, w, h, GetImageHDC(&image), 0, 0, width, height, blendfunc);
}

//繪制旋轉的圖片，支持透明png圖片
void rotate(IMAGE& image, int x, int y, int w, int h, float angle)
{
	//獲取當前繪圖dc
	HDC dc = GetImageHDC();
	//矩陣
	gdimat2 m;
	m.rotate(angle);	//旋轉
	m.translate(x, y);	//平移
	m.use(dc);

	BLENDFUNCTION blendfunc = { AC_SRC_OVER, 0, 255, AC_SRC_ALPHA };
	int width = image.getwidth();
	int height = image.getheight();
	//繪制位置設置圖片的中心點
	x = -w / 2;
	y = -h / 2;
	AlphaBlend(dc, x, y, w, h, GetImageHDC(&image), 0, 0, width, height, blendfunc);

	//初始化矩陣
	m.identity();
	//恢復dc初始變換
	m.use(dc);
}


#endif EX_EASYX_H