mostly working

still some strange things with order3, not initing ddx correctly?

libvips/deprecated/deprecated_dispatch.c

@@ -44,6 +44,27 @@ static im_arg_desc one_in_one_out[] = {
 	IM_OUTPUT_IMAGE( "out" )
 };
 
+static im_arg_desc quadratic_args[] = {
+	IM_INPUT_IMAGE( "in" ),
+	IM_OUTPUT_IMAGE( "out" ),
+	IM_INPUT_IMAGE( "coeff" )
+};
+
+static int
+quadratic_vec( im_object *argv )
+{
+	return( im_quadratic( argv[0], argv[1], argv[2] ) );
+}
+
+static im_function quadratic_desc = {
+	"im_quadratic", 		/* Name */
+	"transform via quadratic",
+	IM_FN_PIO,			/* Flags */
+	quadratic_vec, 			/* Dispatch function */
+	IM_NUMBER( quadratic_args ), 	/* Size of arg list */
+	quadratic_args 			/* Arg list */
+};
+
 /* Two images in, one out.
  */
 static im_arg_desc two_in_one_out[] = {
@@ -2295,7 +2316,8 @@ static im_function *deprecated_list[] = {
 	&moreeqconst_desc,
 	&notequal_desc,
 	&notequal_vec_desc,
-	&notequalconst_desc
+	&notequalconst_desc,
+	&quadratic_desc
 };
 
 /* Package of functions.

libvips/deprecated/vips7compat.c

@@ -2789,3 +2789,20 @@ im_icc_ac2rc( VipsImage *in, VipsImage *out, const char *profile_filename )
 
 	return( 0 );
 }
+
+int 
+im_quadratic( IMAGE *in, IMAGE *out, IMAGE *coeff )
+{
+	VipsImage *x;
+
+	if( vips_quadratic( in, &x, coeff, 
+		NULL ) )
+		return( -1 );
+	if( im_copy( x, out ) ) {
+		g_object_unref( x );
+		return( -1 );
+	}
+	g_object_unref( x );
+
+	return( 0 );
+}

libvips/include/vips/vips7compat.h

@@ -788,6 +788,8 @@ int im_lab_morph( VipsImage *in, VipsImage *out,
 
 #define im_col_dE00 vips_col_dE00
 
+int im_quadratic( IMAGE *in, IMAGE *out, IMAGE *coeff );
+
 /* ruby-vips uses this
  */
 #define vips_class_map_concrete_all vips_class_map_all

libvips/resample/quadratic.c

@@ -52,26 +52,23 @@
 
 #include "resample.h"
 
-/* **************************************************************************
-/@ imtranf.c
-/@
-/@      ALGORITHM
-/@
-/@      x',y' = coordinates of srcim
-/@      x,y   = coordinates of dstim
-/@
-/@
-/@      x = x' + srcvec[0]                     : order 0     image shift only
-/@             + srcvec[2]x'   + srcvec[4]y'   : order 1     + affine transf.
-/@             + srcvec[6]x'y'                 : order 2     + bilinear transf.
-/@             + srcvec[8]x'x' + srcvec[10]y'y': order 3     + quadratic transf.
-/@
-/@      y = y' + srcvec[1]
-/@             + srcvec[3]x'   + srcvec[5]y'
-/@             + srcvec[7]x'y'
-/@             + srcvec[9]x'x' + srcvec[11]y'y'
-/@
-************************************************************************/
+/* The transform we compute:
+
+x',y'  = coordinates of srcim
+x,y    = coordinates of dstim
+a .. l = coefficients
+
+x = x' + a              : order 0     image shift only
+  + b x' + c y'   	: order 1     + affine transf.
+  + d x' y'             : order 2     + bilinear transf.
+  + e x' x' + f y' y'   : order 3     + quadratic transf.
+
+y = y' + g            
+  + h y' + i x'   
+  + j y' x'             
+  + k y' y' + l x' x'  
+
+ */
 
 typedef struct _VipsQuadratic {
 	VipsResample parent_instance;
@@ -203,6 +200,10 @@ vips_quadratic_gen( VipsRegion *or, void *vseq,
 			fyi += vec[5] * yo + vec[3] * xlow;
 			dx += vec[2];
 			dy += vec[3];
+
+		case 0: 
+			/* See above for order 0.
+			 */
 			break;
 
 		default:
@@ -225,7 +226,6 @@ vips_quadratic_gen( VipsRegion *or, void *vseq,
 			if( xi < 0 || xi >= sizex1 || yi < 0 || yi >= sizey1 ) {
 				for( z = 0; z < ps; z++ ) 
 					q[z] = 0;
-				q += ps;
 			}
 			else {
 				/*
@@ -252,6 +252,8 @@ vips_quadratic_gen( VipsRegion *or, void *vseq,
 				TYPE_SWITCH_IPOL;
 			}
 
+			q += ps;
+
 			fxi += dx;
 			fyi += dy;