Writing IWICBtmap to file - incorrect resolution - c++

Question

I have the following code where I read an image (JPG for test), specify a clipping rectangle area and write the "clipped" area out to a file.
My test image is 320 x 240 pixels # 300dpi. When I read it in all indications say that it is that size but when I write it out the result image is 102 x 76 and looking a the file properties I see no H/V resolution.
Now 320/102 = 3.1372 and 300/96 = 3.125 so is there something with screen resolution vs image?
This entire subject of writing out a IWICBitmap has been a boxing match from the beginning. Why is it this hard?
Thanks a bunch
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();
}
More info
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;
The imageRect is correct LTRB = 0,0,320,240
but after the copy wD = 102 and hD = 76
Why?
Here is some more info
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;
The bitmapPixelSize is correct 320 x 240, resX and Y are 300
format= DXGI_FORMAT_B8G8R8A8_UNORM
alphaMode D2D1_ALPHA_MODE_PREMULTIPLIED
wD = 102 and hD = 76 - Why?
Latest code
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();
}

Answer 1

ID2D1Bitmap::GetSize gets you DIPs:
Returns the size, in device-independent pixels (DIPs), of the bitmap.
A DIP is 1/96 of an inch. To retrieve the size in device pixels, use the ID2D1Bitmap::GetPixelSize method.
In your case the size is 320 px * 96 dpi/px / 300 dpi = 102.4 device-independent pixels. The same along Y axis.

Answer 2

Knowing what the original image's resolution is when I create the render target from the WICBitmap I used the following properties
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();
the key was using the resolution of the original image in the create, attempting to set them later did nothing. Roman gave me the "hint" - Thanks