Revert of move erase into SkPixmap (patchset #1 id:1 of https://codereview.chromium.org/1161033005/)

Reason for revert:
broken builds

Original issue's description:
> move erase into SkPixmap
>
> harvested from https://codereview.chromium.org/1148793007
>
> BUG=skia:
> TBR=
>
> Committed: https://skia.googlesource.com/skia/+/0963f5dab079627c5523ce6a443af27a33e361f7

TBR=reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1157303008

1 files changed, 108 insertions, 4 deletions

diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index 49e2c04bfb..f2668f0a20 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -666,8 +666,101 @@ bool SkBitmap::ComputeIsOpaque(const SkBitmap& bm) {
 ///////////////////////////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////////////////////////
 
-void SkBitmap::erase(SkColor c, const SkIRect& area) const {
+static uint16_t pack_8888_to_4444(unsigned a, unsigned r, unsigned g, unsigned b) {
+    unsigned pixel = (SkA32To4444(a) << SK_A4444_SHIFT) |
+                     (SkR32To4444(r) << SK_R4444_SHIFT) |
+                     (SkG32To4444(g) << SK_G4444_SHIFT) |
+                     (SkB32To4444(b) << SK_B4444_SHIFT);
+    return SkToU16(pixel);
+}
+
+static bool internal_erase(const SkPixmap& pmap, const SkIRect& area,
+                           U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
+    int height = area.height();
+    const int width = area.width();
+    const int rowBytes = pmap.rowBytes();
+
+    switch (pmap.colorType()) {
+        case kGray_8_SkColorType: {
+            if (255 != a) {
+                r = SkMulDiv255Round(r, a);
+                g = SkMulDiv255Round(g, a);
+                b = SkMulDiv255Round(b, a);
+            }
+            int gray = SkComputeLuminance(r, g, b);
+            uint8_t* p = pmap.writable_addr8(area.fLeft, area.fTop);
+            while (--height >= 0) {
+                memset(p, gray, width);
+                p += rowBytes;
+            }
+            break;
+        }
+        case kAlpha_8_SkColorType: {
+            uint8_t* p = pmap.writable_addr8(area.fLeft, area.fTop);
+            while (--height >= 0) {
+                memset(p, a, width);
+                p += rowBytes;
+            }
+            break;
+        }
+        case kARGB_4444_SkColorType:
+        case kRGB_565_SkColorType: {
+            uint16_t* p = pmap.writable_addr16(area.fLeft, area.fTop);
+            uint16_t v;
+
+            // make rgb premultiplied
+            if (255 != a) {
+                r = SkAlphaMul(r, a);
+                g = SkAlphaMul(g, a);
+                b = SkAlphaMul(b, a);
+            }
+
+            if (kARGB_4444_SkColorType == pmap.colorType()) {
+                v = pack_8888_to_4444(a, r, g, b);
+            } else {
+                v = SkPackRGB16(r >> (8 - SK_R16_BITS),
+                                g >> (8 - SK_G16_BITS),
+                                b >> (8 - SK_B16_BITS));
+            }
+            while (--height >= 0) {
+                sk_memset16(p, v, width);
+                p = (uint16_t*)((char*)p + rowBytes);
+            }
+            break;
+        }
+        case kBGRA_8888_SkColorType:
+        case kRGBA_8888_SkColorType: {
+            uint32_t* p = pmap.writable_addr32(area.fLeft, area.fTop);
+
+            if (255 != a && kPremul_SkAlphaType == pmap.alphaType()) {
+                r = SkAlphaMul(r, a);
+                g = SkAlphaMul(g, a);
+                b = SkAlphaMul(b, a);
+            }
+            uint32_t v = kRGBA_8888_SkColorType == pmap.colorType() ?
+            SkPackARGB_as_RGBA(a, r, g, b) : SkPackARGB_as_BGRA(a, r, g, b);
+
+            while (--height >= 0) {
+                sk_memset32(p, v, width);
+                p = (uint32_t*)((char*)p + rowBytes);
+            }
+            break;
+        }
+        default:
+            return false; // no change, so don't call notifyPixelsChanged()
+    }
+    return true;
+}
+
+void SkBitmap::internalErase(const SkIRect& area, U8CPU a, U8CPU r, U8CPU g, U8CPU b) const {
+#ifdef SK_DEBUG
     SkDEBUGCODE(this->validate();)
+    SkASSERT(!area.isEmpty());
+    {
+        SkIRect total = { 0, 0, this->width(), this->height() };
+        SkASSERT(total.contains(area));
+    }
+#endif
 
     switch (fInfo.colorType()) {
         case kUnknown_SkColorType:
@@ -683,13 +776,24 @@ void SkBitmap::erase(SkColor c, const SkIRect& area) const {
         return;
     }
 
-    if (result.pixmap().erase(c, area)) {
+    if (internal_erase(result.pixmap(), area, a, r, g, b)) {
         this->notifyPixelsChanged();
     }
 }
 
-void SkBitmap::eraseColor(SkColor c) const {
-    this->erase(c, SkIRect::MakeWH(this->width(), this->height()));
+void SkBitmap::eraseARGB(U8CPU a, U8CPU r, U8CPU g, U8CPU b) const {
+    SkIRect area = { 0, 0, this->width(), this->height() };
+    if (!area.isEmpty()) {
+        this->internalErase(area, a, r, g, b);
+    }
+}
+
+void SkBitmap::eraseArea(const SkIRect& rect, SkColor c) const {
+    SkIRect area = { 0, 0, this->width(), this->height() };
+    if (area.intersect(rect)) {
+        this->internalErase(area, SkColorGetA(c), SkColorGetR(c),
+                            SkColorGetG(c), SkColorGetB(c));
+    }
 }
 
 //////////////////////////////////////////////////////////////////////////////////////