gdi32: Copy gamma ramp validation from winex11 to make it driver independent (try 2)

[André Hentschel]

try2: ERRs downgraded to TRACEs as correctly suggested by Dmitry
---
 dlls/gdi32/dc.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/dlls/gdi32/dc.c b/dlls/gdi32/dc.c
index c6ba488..436758a 100644
--- a/dlls/gdi32/dc.c
+++ b/dlls/gdi32/dc.c
@@ -1311,6 +1311,86 @@ BOOL WINAPI GetDeviceGammaRamp(HDC hDC, LPVOID ptr)
     return ret;
 }
 
+static BOOL check_gamma_ramp(WORD ramp[256])
+{
+    float r_x, r_y, r_lx, r_ly, r_d, r_v, r_e, g_avg, g_min, g_max;
+    unsigned i, f, l, g_n, c;
+
+    f = ramp[0];
+    l = ramp[255];
+    if (f >= l)
+    {
+        TRACE("inverted or flat gamma ramp (%d->%d), rejected\n", f, l);
+        return FALSE;
+    }
+    r_d = l - f;
+    g_min = g_max = g_avg = 0.0;
+
+    /* check gamma ramp entries to estimate the gamma */
+    TRACE("analyzing gamma ramp (%d->%d)\n", f, l);
+    for (i=1, g_n=0; i<255; i++)
+    {
+        if (ramp[i] < f || ramp[i] > l)
+        {
+            TRACE("strange gamma ramp ([%d]=%d for %d->%d), rejected\n", i, ramp[i], f, l);
+            return FALSE;
+        }
+        c = ramp[i] - f;
+        if (!c) continue; /* avoid log(0) */
+
+        /* normalize entry values into 0..1 range */
+        r_x = i/255.0; r_y = c / r_d;
+        /* compute logarithms of values */
+        r_lx = log(r_x); r_ly = log(r_y);
+        /* compute gamma for this entry */
+        r_v = r_ly / r_lx;
+        /* compute differential (error estimate) for this entry */
+        /* some games use table-based logarithms that magnifies the error by 128 */
+        r_e = -r_lx * 128 / (c * r_lx * r_lx);
+
+        /* compute min & max while compensating for estimated error */
+        if (!g_n || g_min > (r_v + r_e)) g_min = r_v + r_e;
+        if (!g_n || g_max < (r_v - r_e)) g_max = r_v - r_e;
+
+        /* add to average */
+        g_avg += r_v;
+        g_n++;
+    }
+
+    if (!g_n)
+    {
+        TRACE("no gamma data, shouldn't happen\n");
+        return FALSE;
+    }
+    g_avg /= g_n;
+    TRACE("low bias is %d, high is %d, gamma is %5.3f\n", f, 65535-l, g_avg);
+
+    /* the bias could be because the app wanted something like a "red shift"
+    * like when you're hit in Quake, but XVidMode doesn't support it,
+    * so we have to reject a significant bias */
+    if (f && f > (pow(1/255.0, g_avg) * 65536.0))
+    {
+        TRACE("low-biased gamma ramp (%d), rejected\n", f);
+        return FALSE;
+    }
+
+    /* check that the gamma is reasonably uniform across the ramp */
+    if (g_max - g_min > 12.8)
+    {
+        TRACE("ramp not uniform (max=%f, min=%f, avg=%f), rejected\n", g_max, g_min, g_avg);
+        return FALSE;
+    }
+
+    /* check that the gamma is not too bright */
+    if (g_avg < 0.2)
+    {
+        TRACE("too bright gamma ( %5.3f), rejected\n", g_avg);
+        return FALSE;
+    }
+
+    return TRUE;
+}
+
 /***********************************************************************
  *           SetDeviceGammaRamp    (GDI32.@)
  */
@@ -1325,6 +1405,18 @@ BOOL WINAPI SetDeviceGammaRamp(HDC hDC, LPVOID ptr)
         if (GetObjectType( hDC ) != OBJ_MEMDC)
         {
             PHYSDEV physdev = GET_DC_PHYSDEV( dc, pSetDeviceGammaRamp );
+            struct gamma_ramp
+            {
+                WORD red[256];
+                WORD green[256];
+                WORD blue[256];
+            } *ramp = ptr;
+
+            if (!check_gamma_ramp(ramp->red) ||
+                !check_gamma_ramp(ramp->green) ||
+                !check_gamma_ramp(ramp->blue))
+                return FALSE;
+
             ret = physdev->funcs->pSetDeviceGammaRamp( physdev, ptr );
         }
         else SetLastError( ERROR_INVALID_PARAMETER );
-- 
1.8.0


-- 

Best Regards, André Hentschel