Swizzler changes Index8 and 565

src/codec/SkSwizzler.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
 #include "SkSwizzler.h"
 #include "SkTemplates.h"
 
 SkSwizzler::ResultAlpha SkSwizzler::GetResult(uint8_t zeroAlpha,
                                               uint8_t maxAlpha) {
     // In the transparent case, this returns 0x0000
     // In the opaque case, this returns 0xFFFF
     // If the row is neither transparent nor opaque, returns something else
     return (((uint16_t) maxAlpha) << 8) | zeroAlpha;
 }
 
 // kIndex1, kIndex2, kIndex4
 
-static SkSwizzler::ResultAlpha swizzle_small_index_to_n32(
+static SkSwizzler::ResultAlpha swizzle_small_index_to_index(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
         int bitsPerPixel, int y, const SkPMColor ctable[]) {
 
-    SkPMColor* SK_RESTRICT dst = (SkPMColor*) dstRow;
+    uint8_t* SK_RESTRICT dst = (uint8_t*) dstRow;
     INIT_RESULT_ALPHA;
     const uint32_t pixelsPerByte = 8 / bitsPerPixel;
     const size_t rowBytes = compute_row_bytes_ppb(width, pixelsPerByte);
     const uint8_t mask = (1 << bitsPerPixel) - 1;
     int x = 0;
     for (uint32_t byte = 0; byte < rowBytes; byte++) {
         uint8_t pixelData = src[byte];
         for (uint32_t p = 0; p < pixelsPerByte && x < width; p++) {
             uint8_t index = (pixelData >> (8 - bitsPerPixel)) & mask;
-            SkPMColor c = ctable[index];
-            UPDATE_RESULT_ALPHA(c >> SK_A32_SHIFT);
-            dst[x] = c;
+            UPDATE_RESULT_ALPHA(ctable[index] >> SK_A32_SHIFT);
+            dst[x] = index;
             pixelData <<= bitsPerPixel;
             x++;
         }
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
-static SkSwizzler::ResultAlpha swizzle_small_index_to_565(
+static SkSwizzler::ResultAlpha swizzle_small_index_to_n32(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
         int bitsPerPixel, int y, const SkPMColor ctable[]) {
 
-    uint16_t* SK_RESTRICT dst = (uint16_t*) dstRow;
+    SkPMColor* SK_RESTRICT dst = (SkPMColor*) dstRow;
+    INIT_RESULT_ALPHA;
     const uint32_t pixelsPerByte = 8 / bitsPerPixel;
     const size_t rowBytes = compute_row_bytes_ppb(width, pixelsPerByte);
     const uint8_t mask = (1 << bitsPerPixel) - 1;
     int x = 0;
     for (uint32_t byte = 0; byte < rowBytes; byte++) {
         uint8_t pixelData = src[byte];
         for (uint32_t p = 0; p < pixelsPerByte && x < width; p++) {
             uint8_t index = (pixelData >> (8 - bitsPerPixel)) & mask;
-            uint16_t c = SkPixel32ToPixel16(ctable[index]);
+            SkPMColor c = ctable[index];
+            UPDATE_RESULT_ALPHA(c >> SK_A32_SHIFT);
             dst[x] = c;
             pixelData <<= bitsPerPixel;
             x++;
         }
     }
-    return SkSwizzler::kOpaque_ResultAlpha;
+    return COMPUTE_RESULT_ALPHA;
+}
+
+static SkSwizzler::ResultAlpha swizzle_index_to_index(
+        void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
+        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+
+    uint8_t* SK_RESTRICT dst = (uint8_t*) dstRow;
+    memcpy(dst, src, width);
+    INIT_RESULT_ALPHA;
+    for (int x = 0; x < width; x++) {
+        UPDATE_RESULT_ALPHA(ctable[src[x]] >> SK_A32_SHIFT);

[scroggo, 2015/04/02 19:20:31]

Interestingly, looking at the old SkScaledBitmapSampler, the analogue
(Sample_Index_DI) just returns false.

I'd be curious to know why that is. The goal of learning whether the image had
alpha is to help us take the fast (opaque) case. It seems like we would still
want to know that when drawing with Index?

[msarett, 2015/04/03 18:01:32]

Hmmm seems like an interesting tradeoff.  It does seem like a shame to loop over
the entire row when all we really need is a memcpy.  However, I wonder if anyone
has actually explored whether it is better to improve performance here in the
decode or when drawing.  Or which performance improvement is more significant.

I think I'll make it a low priority TODO.  Let me know if you want me to imitate
the behavior of SkScaledBitmapSampler for now.

+    }
+    return COMPUTE_RESULT_ALPHA;
 }
 
 // kIndex
 
 static SkSwizzler::ResultAlpha swizzle_index_to_n32(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
         int bytesPerPixel, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
-        SkPMColor c = ctable[*src];
+        SkPMColor c = ctable[src[x]];
         UPDATE_RESULT_ALPHA(c >> SK_A32_SHIFT);
         dst[x] = c;
-        src++;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 static SkSwizzler::ResultAlpha swizzle_index_to_n32_skipZ(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
         int bytesPerPixel, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
-        SkPMColor c = ctable[*src];
+        SkPMColor c = ctable[src[x]];
         UPDATE_RESULT_ALPHA(c >> SK_A32_SHIFT);
         if (c != 0) {
             dst[x] = c;
         }
-        src++;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
-static SkSwizzler::ResultAlpha swizzle_index_to_565(
-        void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
-
-    uint16_t* SK_RESTRICT dst = (uint16_t*)dstRow;
-    for (int x = 0; x < width; x++) {
-        uint16_t c = SkPixel32ToPixel16(ctable[*src]);
-        dst[x] = c;
-        src++;
-    }
-    return SkSwizzler::kOpaque_ResultAlpha;
-}
-
 #undef A32_MASK_IN_PLACE
 
 static SkSwizzler::ResultAlpha swizzle_bgrx_to_n32(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
         int bytesPerPixel, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     for (int x = 0; x < width; x++) {
         dst[x] = SkPackARGB32NoCheck(0xFF, src[2], src[1], src[0]);
         src += bytesPerPixel;
     }
     return SkSwizzler::kOpaque_ResultAlpha;
 }
 
-static SkSwizzler::ResultAlpha swizzle_bgrx_to_565(
-        void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
-
-    uint16_t* SK_RESTRICT dst = (uint16_t*)dstRow;
-    for (int x = 0; x < width; x++) {
-        dst[x] = SkPack888ToRGB16(src[2], src[1], src[0]);
-        src += bytesPerPixel;
-    }
-    return SkSwizzler::kOpaque_ResultAlpha;
-}
-
 // kBGRA
 
 static SkSwizzler::ResultAlpha swizzle_bgra_to_n32_unpremul(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
         int bytesPerPixel, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
         uint8_t alpha = src[3];
@@ skipping 123 matching lines @@
     }
     RowProc proc = NULL;
     switch (sc) {
         case kIndex1:
         case kIndex2:
         case kIndex4:
             switch (info.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_small_index_to_n32;
                     break;
-                case kRGB_565_SkColorType:
-                    proc = &swizzle_small_index_to_565;
+                case kIndex_8_SkColorType:
+                    proc = &swizzle_small_index_to_index;
                     break;
                 default:
                     break;
             }
             break;
         case kIndex:
             switch (info.colorType()) {
                 case kN32_SkColorType:
                     // We assume the color premultiplied ctable (or not) as desired.
                     if (SkImageGenerator::kYes_ZeroInitialized == zeroInit) {
                         proc = &swizzle_index_to_n32_skipZ;
                         break;
                     } else {
                         proc = &swizzle_index_to_n32;
                         break;
                     }
                     break;
-                case kRGB_565_SkColorType:
-                    proc = &swizzle_index_to_565;
+                case kIndex_8_SkColorType:
+                    proc = &swizzle_index_to_index;
                     break;
                 default:
                     break;
             }
             break;
         case kBGR:
         case kBGRX:
             switch (info.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_bgrx_to_n32;
                     break;
-                case kRGB_565_SkColorType:
-                    proc = &swizzle_bgrx_to_565;
-                    break;
                 default:
                     break;
             }
             break;
         case kBGRA:
             switch (info.colorType()) {
                 case kN32_SkColorType:
                     switch (info.alphaType()) {
                         case kUnpremul_SkAlphaType:
                             proc = &swizzle_bgra_to_n32_unpremul;
@@ skipping 96 matching lines @@
     SkASSERT(kConsecutive_NextMode != fNextMode);
     SkDEBUGCODE(fNextMode = kDesignateRow_NextMode);
     
     // Choose the row
     void* row = SkTAddOffset<void>(fDstRow, y*fDstRowBytes);
 
     // Decode the row
     return fRowProc(row, src, fDstInfo.width(), fDeltaSrc, fCurrY,
             fColorTable);
 }