Simplify mirroring code and add tests for non-aliged 1 bit images

Like it is done in Qt 5. Also add the autotest which was completely
missing in Qt 4.

Change-Id: Iaf89272b4e5b7f377c4b2f1ce929661f3d0edd9a
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 109 insertions, 89 deletions

diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 800b886..965a1ba 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -4761,18 +4761,118 @@ QImage QImage::createMaskFromColor(QRgb color, Qt::MaskMode mode) const
 }
 
 
-/*
-  This code is contributed by Philipp Lang,
-  GeneriCom Software Germany (www.generi.com)
-  under the terms of the QPL, Version 1.0
-*/
-
 /*!
     \fn QImage QImage::mirror(bool horizontal, bool vertical) const
 
     Use mirrored() instead.
 */
 
+template<class T> inline void do_mirror_data(QImageData *dst, QImageData *src,
+                                             int dstX0, int dstY0,
+                                             int dstXIncr, int dstYIncr,
+                                             int w, int h)
+{
+    if (dst == src) {
+        // When mirroring in-place, stop in the middle for one of the directions, since we
+        // are swapping the bytes instead of merely copying.
+        const int srcXEnd = dstX0 ? w / 2 : w;
+        const int srcYEnd = !dstX0 && dstY0 ? h / 2 : h;
+        for (int srcY = 0, dstY = dstY0; srcY < srcYEnd; ++srcY, dstY += dstYIncr) {
+            T *srcPtr = (T *) (src->data + srcY * src->bytes_per_line);
+            T *dstPtr = (T *) (dst->data + dstY * dst->bytes_per_line);
+            for (int srcX = 0, dstX = dstX0; srcX < srcXEnd; ++srcX, dstX += dstXIncr)
+                std::swap(srcPtr[srcX], dstPtr[dstX]);
+        }
+    } else {
+        for (int srcY = 0, dstY = dstY0; srcY < h; ++srcY, dstY += dstYIncr) {
+            T *srcPtr = (T *) (src->data + srcY * src->bytes_per_line);
+            T *dstPtr = (T *) (dst->data + dstY * dst->bytes_per_line);
+            for (int srcX = 0, dstX = dstX0; srcX < w; ++srcX, dstX += dstXIncr)
+                dstPtr[dstX] = srcPtr[srcX];
+        }
+    }
+}
+
+inline void do_mirror(QImageData *dst, QImageData *src, bool horizontal, bool vertical)
+{
+    Q_ASSERT(src->width == dst->width && src->height == dst->height && src->depth == dst->depth);
+    int w = src->width;
+    int h = src->height;
+    int depth = src->depth;
+
+    if (src->depth == 1) {
+        w = (w + 7) / 8; // byte aligned width
+        depth = 8;
+    }
+
+    int dstX0 = 0, dstXIncr = 1;
+    int dstY0 = 0, dstYIncr = 1;
+    if (horizontal) {
+        // 0 -> w-1, 1 -> w-2, 2 -> w-3, ...
+        dstX0 = w - 1;
+        dstXIncr = -1;
+    }
+    if (vertical) {
+        // 0 -> h-1, 1 -> h-2, 2 -> h-3, ...
+        dstY0 = h - 1;
+        dstYIncr = -1;
+    }
+
+    switch (depth) {
+    case 32:
+        do_mirror_data<quint32>(dst, src, dstX0, dstY0, dstXIncr, dstYIncr, w, h);
+        break;
+    case 24:
+        do_mirror_data<quint24>(dst, src, dstX0, dstY0, dstXIncr, dstYIncr, w, h);
+        break;
+    case 16:
+        do_mirror_data<quint16>(dst, src, dstX0, dstY0, dstXIncr, dstYIncr, w, h);
+        break;
+    case 8:
+        do_mirror_data<quint8>(dst, src, dstX0, dstY0, dstXIncr, dstYIncr, w, h);
+        break;
+    default:
+        Q_ASSERT(false);
+        break;
+    }
+
+    // The bytes are now all in the correct place. In addition, the bits in the individual
+    // bytes have to be flipped too when horizontally mirroring a 1 bit-per-pixel image.
+    if (horizontal && dst->depth == 1) {
+        Q_ASSERT(dst->format == QImage::Format_Mono || dst->format == QImage::Format_MonoLSB);
+        const int shift = 8 - (dst->width % 8);
+        const uchar *bitflip = qt_get_bitflip_array();
+        for (int y = 0; y < h; ++y) {
+            uchar *begin = dst->data + y * dst->bytes_per_line;
+            uchar *end = begin + dst->bytes_per_line;
+            for (uchar *p = begin; p < end; ++p) {
+                *p = bitflip[*p];
+                // When the data is non-byte aligned, an extra bit shift (of the number of
+                // unused bits at the end) is needed for the entire scanline.
+                if (shift != 8 && p != begin) {
+                    if (dst->format == QImage::Format_Mono) {
+                        for (int i = 0; i < shift; ++i) {
+                            p[-1] <<= 1;
+                            p[-1] |= (*p & (128 >> i)) >> (7 - i);
+                        }
+                    } else {
+                        for (int i = 0; i < shift; ++i) {
+                            p[-1] >>= 1;
+                            p[-1] |= (*p & (1 << i)) << (7 - i);
+                        }
+                    }
+                }
+            }
+            if (shift != 8) {
+                if (dst->format == QImage::Format_Mono)
+                    end[-1] <<= shift;
+                else
+                    end[-1] >>= shift;
+            }
+        }
+    }
+}
+
 /*!
     Returns a mirror of the image, mirrored in the horizontal and/or
     the vertical direction depending on whether \a horizontal and \a
@@ -4790,8 +4890,6 @@ QImage QImage::mirrored(bool horizontal, bool vertical) const
     if ((d->width <= 1 && d->height <= 1) || (!horizontal && !vertical))
         return *this;
 
-    int w = d->width;
-    int h = d->height;
     // Create result image, copy colormap
     QImage result(d->width, d->height, d->format);
     QIMAGE_SANITYCHECK_MEMORY(result);
@@ -4802,88 +4900,10 @@ QImage QImage::mirrored(bool horizontal, bool vertical) const
 
     result.d->colortable = d->colortable;
     result.d->has_alpha_clut = d->has_alpha_clut;
+    result.d->dpmx = d->dpmx;
+    result.d->dpmy = d->dpmy;
 
-    if (depth() == 1)
-        w = (w+7)/8;
-    int dxi = horizontal ? -1 : 1;
-    int dxs = horizontal ? w-1 : 0;
-    int dyi = vertical ? -1 : 1;
-    int dy = vertical ? h-1: 0;
-
-    // 1 bit, 8 bit
-    if (d->depth == 1 || d->depth == 8) {
-        for (int sy = 0; sy < h; sy++, dy += dyi) {
-            quint8* ssl = (quint8*)(d->data + sy*d->bytes_per_line);
-            quint8* dsl = (quint8*)(result.d->data + dy*result.d->bytes_per_line);
-            int dx = dxs;
-            for (int sx = 0; sx < w; sx++, dx += dxi)
-                dsl[dx] = ssl[sx];
-        }
-    }
-    // 16 bit
-    else if (d->depth == 16) {
-        for (int sy = 0; sy < h; sy++, dy += dyi) {
-            quint16* ssl = (quint16*)(d->data + sy*d->bytes_per_line);
-            quint16* dsl = (quint16*)(result.d->data + dy*result.d->bytes_per_line);
-            int dx = dxs;
-            for (int sx = 0; sx < w; sx++, dx += dxi)
-                dsl[dx] = ssl[sx];
-        }
-    }
-    // 24 bit
-    else if (d->depth == 24) {
-        for (int sy = 0; sy < h; sy++, dy += dyi) {
-            quint24* ssl = (quint24*)(d->data + sy*d->bytes_per_line);
-            quint24* dsl = (quint24*)(result.d->data + dy*result.d->bytes_per_line);
-            int dx = dxs;
-            for (int sx = 0; sx < w; sx++, dx += dxi)
-                dsl[dx] = ssl[sx];
-        }
-    }
-    // 32 bit
-    else if (d->depth == 32) {
-        for (int sy = 0; sy < h; sy++, dy += dyi) {
-            quint32* ssl = (quint32*)(d->data + sy*d->bytes_per_line);
-            quint32* dsl = (quint32*)(result.d->data + dy*result.d->bytes_per_line);
-            int dx = dxs;
-            for (int sx = 0; sx < w; sx++, dx += dxi)
-                dsl[dx] = ssl[sx];
-        }
-    }
-
-    // special handling of 1 bit images for horizontal mirroring
-    if (horizontal && d->depth == 1) {
-        int shift = width() % 8;
-        for (int y = h-1; y >= 0; y--) {
-            quint8* a0 = (quint8*)(result.d->data + y*d->bytes_per_line);
-            // Swap bytes
-            quint8* a = a0+dxs;
-            while (a >= a0) {
-                *a = bitflip[*a];
-                a--;
-            }
-            // Shift bits if unaligned
-            if (shift != 0) {
-                a = a0+dxs;
-                quint8 c = 0;
-                if (format() == Format_MonoLSB) {
-                    while (a >= a0) {
-                        quint8 nc = *a << shift;
-                        *a = (*a >> (8-shift)) | c;
-                        --a;
-                        c = nc;
-                    }
-                } else {
-                    while (a >= a0) {
-                        quint8 nc = *a >> shift;
-                        *a = (*a << (8-shift)) | c;
-                        --a;
-                        c = nc;
-                    }
-                }
-            }
-        }
-    }
+    do_mirror(result.d, d, horizontal, vertical);
 
     return result;
 }