Improve documentation of FPDF_RenderPageBitmapWithMatrix.
Change-Id: I5cb28dfd6b1e5670fc20093c5d2f9757ad6a4060
Reviewed-on: https://pdfium-review.googlesource.com/22830
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
diff --git a/public/fpdfview.h b/public/fpdfview.h
index 1cd3d6d..6978012 100644
--- a/public/fpdfview.h
+++ b/public/fpdfview.h
@@ -112,7 +112,14 @@
// system wide string by yourself.
typedef const char* FPDF_STRING;
-// Matrix for transformation.
+// Matrix for transformation, in the form [a b c d e f], equivalent to:
+// | a b 0 |
+// | c d 0 |
+// | e f 1 |
+//
+// Translation is performed with [1 0 0 1 tx ty].
+// Scaling is performed with [sx 0 0 sy 0 0].
+// See PDF Reference 1.7, 4.2.2 Common Transformations for more.
typedef struct _FS_MATRIX_ {
float a;
float b;
@@ -667,9 +674,10 @@
// output buffer). The bitmap handle can be created
// by FPDFBitmap_Create or retrieved by
// FPDFImageObj_GetBitmap.
-// page - Handle to the page. Returned by FPDF_LoadPage
-// matrix - The transform matrix. It must be invertible.
-// clipping - The rect to clip to.
+// page - Handle to the page. Returned by FPDF_LoadPage.
+// matrix - The transform matrix, which must be invertible.
+// See PDF Reference 1.7, 4.2.2 Common Transformations.
+// clipping - The rect to clip to in page coords.
// flags - 0 for normal display, or combination of the Page
// Rendering flags defined above. With the FPDF_ANNOT
// flag, it renders all annotations that do not require
