(#92) Fix application of scale factor when calculating actual image sizes for screen grabs

Author: s1hofmann

src/win32/screengrab.c

@@ -2,7 +2,8 @@
 #include "../endian.h"
 #include <stdlib.h> /* malloc() */
 
-MMRect getScaledRect(MMRect input, HDC imageSource) {
+MMRect getScaledRect(MMRect input)
+{
 	// Configure DPI awareness to fetch unscaled display size
 	DPI_AWARENESS_CONTEXT initialDpiAwareness = SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2);
 	size_t scaledDesktopWidth = (size_t)GetSystemMetrics(SM_CXSCREEN);
@@ -15,7 +16,7 @@ MMRect getScaledRect(MMRect input, HDC imageSource) {
 	double scaleX = (double)(desktopWidth / (double)scaledDesktopWidth);
 	double scaleY = (double)(desktopHeight / (double)scaledDesktopHeight);
 
-	return MMRectMake(input.origin.x, input.origin.y, input.size.width * scaleX, input.size.height * scaleY);
+	return MMRectMake(input.origin.x, input.origin.y, input.size.width / scaleX, input.size.height / scaleY);
 }
 
 MMBitmapRef copyMMBitmapFromDisplayInRect(MMRect rect)
@@ -27,56 +28,62 @@ MMBitmapRef copyMMBitmapFromDisplayInRect(MMRect rect)
 	BITMAPINFO bi;
 
 	screen = GetWindowDC(NULL); /* Get entire screen */
-	MMRect scaledRect = getScaledRect(rect, screen);
+	MMRect scaledRect = getScaledRect(rect);
 
-	if (screen == NULL) return NULL;
+	if (screen == NULL) {
+		return NULL;
+	}
 
 	/* Initialize bitmap info. */
 	bi.bmiHeader.biSize = sizeof(bi.bmiHeader);
-   	bi.bmiHeader.biWidth = (long)scaledRect.size.width;
-   	bi.bmiHeader.biHeight = -(long)scaledRect.size.height; /* Non-cartesian, please */
-   	bi.bmiHeader.biPlanes = 1;
-   	bi.bmiHeader.biBitCount = 32;
-   	bi.bmiHeader.biCompression = BI_RGB;
-   	bi.bmiHeader.biSizeImage = (DWORD)(4 * scaledRect.size.width * scaledRect.size.height);
+	bi.bmiHeader.biWidth = (long)scaledRect.size.width;
+	bi.bmiHeader.biHeight = -(long)scaledRect.size.height; /* Non-cartesian, please */
+	bi.bmiHeader.biPlanes = 1;
+	bi.bmiHeader.biBitCount = 32;
+	bi.bmiHeader.biCompression = BI_RGB;
+	bi.bmiHeader.biSizeImage = (DWORD)(4 * scaledRect.size.width * scaledRect.size.height);
 	bi.bmiHeader.biXPelsPerMeter = 0;
 	bi.bmiHeader.biYPelsPerMeter = 0;
 	bi.bmiHeader.biClrUsed = 0;
 	bi.bmiHeader.biClrImportant = 0;
 
 	/* Get screen data in display device context. */
-   	dib = CreateDIBSection(screen, &bi, DIB_RGB_COLORS, &data, NULL, 0);
+	dib = CreateDIBSection(screen, &bi, DIB_RGB_COLORS, &data, NULL, 0);
 
 	/* Copy the data into a bitmap struct. */
 	if ((screenMem = CreateCompatibleDC(screen)) == NULL ||
 	    SelectObject(screenMem, dib) == NULL ||
 	    !BitBlt(screenMem,
-	            (int)0,
-	            (int)0,
-	            (int)scaledRect.size.width,
-	            (int)scaledRect.size.height,
-				screen,
-				(int)scaledRect.origin.x,
-				(int)scaledRect.origin.y,
-				SRCCOPY)) {
-		
+		    (int)0,
+		    (int)0,
+		    (int)scaledRect.size.width,
+		    (int)scaledRect.size.height,
+		    screen,
+		    (int)scaledRect.origin.x,
+		    (int)scaledRect.origin.y,
+		    SRCCOPY))
+	{
+
 		/* Error copying data. */
 		ReleaseDC(NULL, screen);
 		DeleteObject(dib);
-		if (screenMem != NULL) DeleteDC(screenMem);
+		if (screenMem != NULL) {
+			DeleteDC(screenMem);
+		}
 
 		return NULL;
 	}
 
 	bitmap = createMMBitmap(NULL,
-	                        scaledRect.size.width,
-	                        scaledRect.size.height,
-	                        4 * scaledRect.size.width,
-	                        (uint8_t)bi.bmiHeader.biBitCount,
-	                        4);
+				scaledRect.size.width,
+				scaledRect.size.height,
+				4 * scaledRect.size.width,
+				(uint8_t)bi.bmiHeader.biBitCount,
+				4);
 
 	/* Copy the data to our pixel buffer. */
-	if (bitmap != NULL) {
+	if (bitmap != NULL)
+	{
 		bitmap->imageBuffer = malloc(bitmap->bytewidth * bitmap->height);
 		memcpy(bitmap->imageBuffer, data, bitmap->bytewidth * bitmap->height);
 	}