请问在缩放时候如何控制从图片的中央缩放，而不是左上角开始缩放，具体请看Skydrive上的Demo

Question

请问在缩放时候如何控制从图片的中央缩放，而不是左上角开始缩放，具体请看Skydrive上的Demo

上述demo的效果是缩放和平移在图片的范围；

目前缩放只能从左上角开始，但是我需要缩放图片是从图片的正面开始缩放，请问如何才能控制呢？

	D2D1_MATRIX_3X2_F scale = D2D1::Matrix3x2F::Scale(D2D1::SizeF(m_dScale, m_dScale), D2D1::Point2F(0.0f, 0.0f));
	D2D1_MATRIX_3X2_F translation = D2D1::Matrix3x2F::Translation(m_iOffsetX, m_iOffsetY);
	g_pRenderTarget->SetTransform(scale* translation);

	D2D1_POINT_2F upperLeftCorner = D2D1::Point2F(0.0f, 0.0f);
	// Draw bitmap
	g_pRenderTarget->DrawBitmap(
		g_pBitmap,
		D2D1::RectF(
		upperLeftCorner.x,
		upperLeftCorner.y,
		upperLeftCorner.x + size.width,
		upperLeftCorner.y + size.height)
		);

我Demo的下载地址如下：（注：运行时需要GyrometerSensor）

Demo是：ZoomPanDesktopD2DApp.7z文件

https://onedrive.live.com/?cid=d2327ea047e691b7#cid=D2327EA047E691B7&id=D2327EA047E691B7%21105

Answer 1

请求大神帮助，我不知道如何才能得到我想要的缩放效果；

现在是从左上角开始缩放;我想要的是从图片正面的中心开始缩放

Answer 2

说明：在屏幕上保持2个TouchPoint就能进入Zoom模式;保持1个TouchPoint就能进入Pan模式

Answer 3

我已经修复Issue，抱歉打扰

Answer 4

你好，

请问你是如何解决的，能否分享一下你的方案，十分感谢。

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Answer 5

void ZoomPanImage()
{
	if (m_dScale > 1)
	{
		if (m_dScale > 4)
			m_dScale = 4;
	}

	CreateD2DResource(g_Hwnd);

	g_pRenderTarget->BeginDraw();

	// Clear background color to white
	g_pRenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::White));
	D2D1_SIZE_F size = g_pBitmap->GetSize();

	float availX = static_cast<float>(size.width  * (m_dScale - 1));
	float availY = static_cast<float>(size.height * (m_dScale - 1));

	if (m_iOffsetX >= availX/2)
	{
		m_iOffsetX = availX / 2;
	}
	else if (m_iOffsetX <= -availX / 2)
	{
		m_iOffsetX = -availX / 2;
	}
	else if ((m_iOffsetX < availX / 2) && (m_iOffsetX > -availX / 2))
	{
	}

	if (m_iOffsetY >= availY / 2)
	{
		m_iOffsetY = availY / 2;
	}
	else if (m_iOffsetY <= -availY / 2)
	{
		m_iOffsetY = -availY / 2;
	}
	else if ((m_iOffsetY < availY / 2) && (m_iOffsetY > -availY / 2))
	{
	}

	D2D1_MATRIX_3X2_F scale = D2D1::Matrix3x2F::Scale(D2D1::SizeF(m_dScale, m_dScale), D2D1::Point2F(size.width / 2, size.height / 2));
	D2D1_MATRIX_3X2_F translation = D2D1::Matrix3x2F::Translation(m_iOffsetX, m_iOffsetY);
	g_pRenderTarget->SetTransform(scale* translation);

	D2D1_POINT_2F upperLeftCorner = D2D1::Point2F(0.f, 0.f);
	// Draw bitmap
	g_pRenderTarget->DrawBitmap(
		g_pBitmap,
		D2D1::RectF(
		upperLeftCorner.x,
		upperLeftCorner.y,
		upperLeftCorner.x + size.width,
		upperLeftCorner.y + size.height)
		);

	HRESULT hr = g_pRenderTarget->EndDraw();
	if (FAILED(hr))
	{
		MessageBox(NULL, "Draw failed!", "Error", 0);
		return;
	}
}

Answer 6

缩放的时候注意CenterPoint与缩放时候的边界范围就好了