Add SkImageInfoValidConversion() and SkImageInfoIsValid

The idea is share these standards for the following:
SkImage::readPixels()
SkCanvas::readPixels()
SkCanvas::writePixels()
SkBitmap::readPixels()
SkPixmap::readPixels()

On the raster side, SkPixmap::readPixels() is the right
place to check, because all raster calls go through
there eventually.  Then at lower levels (ex: SkPixelInfo),
we can assert.

There's not really a unifying location for gpu calls,
so I've added this in multiple places.  I haven't really
dug into the gpu code to SkASSERT() on invalid cases
that we will have already caught.

Follow-up work:
Similar refactor for SkReadPixelRec::trim().
Code cleanup in SkPixelInfo::CopyPixels()

BUG=skia:6021

Change-Id: I91ecce10e46c1a6530f0af24a9eb8226dbecaaa2
Reviewed-on: https://skia-review.googlesource.com/6887
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Reed <reed@google.com>

1 files changed, 41 insertions, 1 deletions

diff --git a/gm/showmiplevels.cpp b/gm/showmiplevels.cpp
index a4fd16404f..0394b57318 100644
--- a/gm/showmiplevels.cpp
+++ b/gm/showmiplevels.cpp
@@ -216,6 +216,46 @@ DEF_GM( return new ShowMipLevels(256); )
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
+static void copy_32_to_g8(void* dst, size_t dstRB, const void* src, const SkImageInfo& srcInfo,
+                          size_t srcRB) {
+    uint8_t* dst8 = (uint8_t*)dst;
+    const uint32_t* src32 = (const uint32_t*)src;
+
+    const int w = srcInfo.width();
+    const int h = srcInfo.height();
+    const bool isBGRA = (kBGRA_8888_SkColorType == srcInfo.colorType());
+
+    for (int y = 0; y < h; ++y) {
+        if (isBGRA) {
+            // BGRA
+            for (int x = 0; x < w; ++x) {
+                uint32_t s = src32[x];
+                dst8[x] = SkComputeLuminance((s >> 16) & 0xFF, (s >> 8) & 0xFF, s & 0xFF);
+            }
+        } else {
+            // RGBA
+            for (int x = 0; x < w; ++x) {
+                uint32_t s = src32[x];
+                dst8[x] = SkComputeLuminance(s & 0xFF, (s >> 8) & 0xFF, (s >> 16) & 0xFF);
+            }
+        }
+        src32 = (const uint32_t*)((const char*)src32 + srcRB);
+        dst8 += dstRB;
+    }
+}
+
+void copy_to(SkBitmap* dst, SkColorType dstColorType, const SkBitmap& src) {
+    if (kGray_8_SkColorType == dstColorType) {
+        SkImageInfo grayInfo = src.info().makeColorType(kGray_8_SkColorType);
+        dst->allocPixels(grayInfo);
+        copy_32_to_g8(dst->getPixels(), dst->rowBytes(), src.getPixels(), src.info(),
+                      src.rowBytes());
+        return;
+    }
+
+    src.copyTo(dst, dstColorType);
+}
+
 /**
  *  Show mip levels that were built, for all supported colortypes
  */
@@ -283,7 +323,7 @@ protected:
 
         for (auto ctype : ctypes) {
             SkBitmap bm;
-            orig.copyTo(&bm, ctype);
+            copy_to(&bm, ctype, orig);
             drawLevels(canvas, bm);
             canvas->translate(orig.width()/2 + 8.0f, 0);
         }