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我有以下代码，我在其中读取图像（用于测试的 JPG），指定剪切矩形区域并将“剪切”区域写入文件。

我的测试图像是 320 x 240 像素 @ 300dpi。当我在所有迹象中阅读它时都说它是那个大小但是当我把它写出来时结果图像是 102 x 76 并且查看文件属性我看不到 H/V 分辨率。

现在 320/102 = 3.1372 和 300/96 = 3.125 那么屏幕分辨率与图像有什么关系吗？

写出 IWICBitmap 的整个主题从一开始就是一场拳击比赛。为什么这么难？

谢谢一堆

IWICImagingFactory *pImageFactory = GfxAgent::WICImagingFactory::GetInstance().GetFactory();

   D2D1_SIZE_U sizeFrame = D2D1::SizeU(imageRect.Width(), imageRect.Height());

   CComPtr<IWICBitmap> pWICBitmap;
   hr = pImageFactory->CreateBitmap(imageRect.Width(), imageRect.Height(),
      GUID_WICPixelFormat32bppPBGRA,
      WICBitmapCacheOnLoad,
      &pWICBitmap
      );

   D2D1_RENDER_TARGET_PROPERTIES rtProps = D2D1::RenderTargetProperties();
   rtProps.pixelFormat = D2D1::PixelFormat(DXGI_FORMAT_B8G8R8A8_UNORM, D2D1_ALPHA_MODE_PREMULTIPLIED);
   rtProps.type = D2D1_RENDER_TARGET_TYPE_DEFAULT;
   rtProps.usage = D2D1_RENDER_TARGET_USAGE_NONE;

   // define the render target
   CComPtr<ID2D1RenderTarget> pRenderTarget = 0;
   hr = m_pDirect2dFactory->CreateWicBitmapRenderTarget(pWICBitmap, rtProps, &pRenderTarget);

   CComPtr<ID2D1Bitmap> imageS;
   hr = GfxAgent::ImageUtilities::LoadImageFromFile(pRenderTarget, m_imgPath, 0, 0, 0, &imageS, &resX, &resY);

   if (hr != S_OK)
   {
   }

   // get format of image we just read
   D2D1_PIXEL_FORMAT fmt = imageS->GetPixelFormat();

   CComPtr<ID2D1Bitmap> imageD;
   D2D1_SIZE_U bitmapPixelSize = D2D1::SizeU(imageRect.Width(), imageRect.Height());

   // create destination image of "clipped" source image
   hr = pRenderTarget->CreateBitmap(bitmapPixelSize, D2D1::BitmapProperties(
      D2D1::PixelFormat(fmt.format, fmt.alphaMode),
      (float)resX, (float)resY), &imageD);

   D2D1_POINT_2U topleft = D2D1::Point2U(0, 0);
   D2D1_RECT_U srcRect = D2D1::RectU(imageRect.left, imageRect.top, imageRect.right, imageRect.bottom);
   // get the "clipped" source
   hr = imageD->CopyFromBitmap(&topleft, imageS, &srcRect);

   if (hr != S_OK)
   {
   }

   CComPtr<IWICBitmapEncoder> pEncoder;
   CComPtr<IWICBitmapFrameEncode> pFrame;
   CComPtr<IWICStream> pStream;

   WICPixelFormatGUID format = GUID_WICPixelFormat32bppPBGRA;

   // draw the "clipped" image into the render target (WIC image)
   if (SUCCEEDED(hr)) {
      pRenderTarget->BeginDraw();
      pRenderTarget->Clear();
      pRenderTarget->DrawBitmap(imageD);
      hr = pRenderTarget->EndDraw();
   }

   // now proceed to write the "clipped" image to a file
   if (SUCCEEDED(hr)) {
      hr = pImageFactory->CreateStream(&pStream);
   }

   if (SUCCEEDED(hr)) {
      hr = pStream->InitializeFromFilename(MultiByteToUnicode(szNewFileName).c_str(), GENERIC_WRITE);
   }

   if (SUCCEEDED(hr)) {
      hr = pImageFactory->CreateEncoder(GUID_ContainerFormatJpeg, NULL, &pEncoder);
   }

   if (SUCCEEDED(hr)) {
      hr = pEncoder->Initialize(pStream, WICBitmapEncoderNoCache);
   }

   if (SUCCEEDED(hr)) {
      hr = pEncoder->CreateNewFrame(&pFrame, NULL);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->Initialize(NULL);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->SetSize((UINT)imageD->GetSize().width, (UINT)imageD->GetSize().height);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->SetPixelFormat(&format);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->WriteSource(pWICBitmap, NULL);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->Commit();
   }

   if (SUCCEEDED(hr)) {
      hr = pEncoder->Commit();
   }

更多信息

      D2D1_POINT_2U topleft = D2D1::Point2U(0, 0);
   D2D1_RECT_U srcRect = D2D1::RectU(imageRect.left, imageRect.top, imageRect.right, imageRect.bottom);
   // get the "clipped" source
   hr = imageD->CopyFromBitmap(&topleft, imageS, &srcRect);

   if (hr != S_OK)
   {
   }

   UINT wD, hD;
   wD = (UINT)imageD->GetSize().width;
   hD = (UINT)imageD->GetSize().height;

imageRect 是正确的 LTRB = 0,0,320,240

但复制后 wD = 102 和 hD = 76

为什么？

这是更多信息

CComPtr<ID2D1Bitmap> imageD;
   D2D1_SIZE_U bitmapPixelSize = D2D1::SizeU(imageRect.Width(), imageRect.Height());

   // create destination image of "clipped" source image
   hr = pRenderTarget->CreateBitmap(bitmapPixelSize, D2D1::BitmapProperties(
      D2D1::PixelFormat(fmt.format, fmt.alphaMode),
      (float)resX, (float)resY), &imageD);

   UINT wD, hD;
   wD = (UINT)imageD->GetSize().width;
   hD = (UINT)imageD->GetSize().height;

bitmapPixelSize 是正确的 320 x 240，resX 和 Y 是 300

    format= DXGI_FORMAT_B8G8R8A8_UNORM
    alphaMode   D2D1_ALPHA_MODE_PREMULTIPLIED

wD = 102 和 hd = 76 - 为什么？

最新代码

IWICImagingFactory *pImageFactory = GfxAgent::WICImagingFactory::GetInstance().GetFactory();

   D2D1_SIZE_U sizeFrame = D2D1::SizeU(imageRect.Width(), imageRect.Height());

   CComPtr<IWICBitmap> pWICBitmap;
   hr = pImageFactory->CreateBitmap(imageRect.Width(), imageRect.Height(),
      GUID_WICPixelFormat32bppPBGRA,
      WICBitmapCacheOnLoad,
      &pWICBitmap
      );

   // sanity check
   UINT wicW, wicH;
   pWICBitmap->GetSize(&wicW, &wicH);

   D2D1_RENDER_TARGET_PROPERTIES rtProps = D2D1::RenderTargetProperties();
   rtProps.pixelFormat = D2D1::PixelFormat(DXGI_FORMAT_B8G8R8A8_UNORM, D2D1_ALPHA_MODE_PREMULTIPLIED);
   rtProps.type = D2D1_RENDER_TARGET_TYPE_DEFAULT;
   rtProps.usage = D2D1_RENDER_TARGET_USAGE_NONE;

   // define the render target
   CComPtr<ID2D1RenderTarget> pRenderTarget = 0;
   hr = m_pDirect2dFactory->CreateWicBitmapRenderTarget(pWICBitmap, rtProps, &pRenderTarget);

   CComPtr<ID2D1Bitmap> imageS;
   hr = GfxAgent::ImageUtilities::LoadImageFromFile(pRenderTarget, m_imgPath, 0, 0, 0, &imageS, &resX, &resY);

   if (hr != S_OK)
   {
   }

   // set new image resolution same as source
   pWICBitmap->SetResolution(resX, resY);

   // get format of image we just read
   D2D1_PIXEL_FORMAT fmt = imageS->GetPixelFormat();

   CComPtr<ID2D1Bitmap> imageD;
   D2D1_SIZE_U bitmapPixelSize = D2D1::SizeU(imageRect.Width(), imageRect.Height());

   // create destination image of "clipped" source image
   hr = pRenderTarget->CreateBitmap(bitmapPixelSize, D2D1::BitmapProperties(
      D2D1::PixelFormat(fmt.format, fmt.alphaMode),
      (float)resX, (float)resY), &imageD);

   D2D1_POINT_2U topleft = D2D1::Point2U(0, 0);
   D2D1_RECT_U srcRect = D2D1::RectU(imageRect.left, imageRect.top, imageRect.right, imageRect.bottom);
   // get the "clipped" source
   hr = imageD->CopyFromBitmap(&topleft, imageS, &srcRect);

   if (hr != S_OK)
   {
   }

   // just a sanity check (pixels NOT DIPS)
   D2D1_SIZE_U sourcePixelSize = imageS->GetPixelSize();
   D2D1_SIZE_U destPixelSize = imageD->GetPixelSize();

   CComPtr<IWICBitmapEncoder> pEncoder;
   CComPtr<IWICBitmapFrameEncode> pFrame;
   CComPtr<IWICStream> pStream;

   WICPixelFormatGUID format = GUID_WICPixelFormat32bppPBGRA;

   // draw the "clipped" image into the render target (WIC image)
   if (SUCCEEDED(hr)) {
      pRenderTarget->BeginDraw();
      pRenderTarget->Clear();
      pRenderTarget->DrawBitmap(imageD);
      hr = pRenderTarget->EndDraw();
   }

   // now proceed to write the "clipped" image to a file
   if (SUCCEEDED(hr)) {
      hr = pImageFactory->CreateStream(&pStream);
   }

   if (SUCCEEDED(hr)) {
      hr = pStream->InitializeFromFilename(MultiByteToUnicode(szNewFileName).c_str(), GENERIC_WRITE);
   }

   if (SUCCEEDED(hr)) {
      hr = pImageFactory->CreateEncoder(GUID_ContainerFormatJpeg, NULL, &pEncoder);
   }

   if (SUCCEEDED(hr)) {
      hr = pEncoder->Initialize(pStream, WICBitmapEncoderNoCache);
   }

   if (SUCCEEDED(hr)) {
      hr = pEncoder->CreateNewFrame(&pFrame, NULL);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->Initialize(NULL);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->SetSize(destPixelSize.width, destPixelSize.height);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->SetPixelFormat(&format);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->WriteSource(pWICBitmap, NULL);
   }

   if (SUCCEEDED(hr)) {
      hr = pFrame->Commit();
   }

   if (SUCCEEDED(hr)) {
      hr = pEncoder->Commit();
   }
4

2 回答 2

1

ID2D1Bitmap::GetSize让你 DIP：

返回位图的大小，以与设备无关的像素 (DIP) 为单位。

DIP 是 1/96 英寸。要检索设备像素的大小，请使用 ID2D1Bitmap::GetPixelSize 方法。

在您的情况下，大小为 320 px * 96 dpi/px / 300 dpi = 102.4 与设备无关的像素。沿 Y 轴相同。

于 2015-02-02T14:39:44.147 回答
0

当我从 WICBitmap 创建渲染目标时，知道原始图像的分辨率是多少，我使用了以下属性

   D2D1_RENDER_TARGET_PROPERTIES rtProps = D2D1::RenderTargetProperties();
   rtProps.pixelFormat = D2D1::PixelFormat(DXGI_FORMAT_B8G8R8A8_UNORM, D2D1_ALPHA_MODE_PREMULTIPLIED);
   rtProps.type = D2D1_RENDER_TARGET_TYPE_DEFAULT;
   rtProps.usage = D2D1_RENDER_TARGET_USAGE_NONE;
   rtProps.dpiX = (float)m_img.GetResolutionX();
   rtProps.dpiY = (float)m_img.GetResolutionY();

关键是在创建中使用原始图像的分辨率，稍后尝试设置它们什么也没做。罗马给了我“提示” - 谢谢

于 2015-02-09T18:48:21.527 回答