SkScaledCodec class

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"
 #include "SkUtils.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;
 }
 
+static SkSwizzler::ResultAlpha sample(void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src,
+                                      int width, int deltaSrc, int y, const SkPMColor ctable[]){
+    uint8_t* SK_RESTRICT dst = (uint8_t*) dstRow;
+    for (int x = 0; x < width; x++) {
+        dst[x] = src[0];
+        src += deltaSrc;
+    }
+}
 // kIndex1, kIndex2, kIndex4
 
 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[]) {
 
     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);
@@ skipping 33 matching lines @@
             x++;
         }
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 // kIndex
 
 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[]) {
+        int deltaSrc, int y, const SkPMColor ctable[]) {
 
     uint8_t* SK_RESTRICT dst = (uint8_t*) dstRow;
-    memcpy(dst, src, width);
+    if (1 == deltaSrc) {
+        memcpy(dst, src, width);
+    } else {
+        for (int x = 0; x < width; x++) {
+            dst[x] = src[0];
+            src += deltaSrc;
+        }
+    }
     // TODO (msarett): Should we skip the loop here and guess that the row is opaque/not opaque?
     //                 SkScaledBitmap sampler just guesses that it is opaque.  This is dangerous
     //                 and probably wrong since gif and bmp (rarely) may have alpha.
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
         UPDATE_RESULT_ALPHA(ctable[src[x]] >> SK_A32_SHIFT);
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 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[]) {
+        int deltaSrc, 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[x]];
+        SkPMColor c = ctable[*src];
         UPDATE_RESULT_ALPHA(c >> SK_A32_SHIFT);
         dst[x] = c;
+        src += deltaSrc;
     }
     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[]) {
+        int deltaSrc, 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[x]];
+        SkPMColor c = ctable[*src];
         UPDATE_RESULT_ALPHA(c >> SK_A32_SHIFT);
         if (c != 0) {
             dst[x] = c;
         }
+        src += deltaSrc;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 #undef A32_MASK_IN_PLACE
 
 // kGray
 
 static SkSwizzler::ResultAlpha swizzle_gray_to_n32(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+        int deltaSrc, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     for (int x = 0; x < width; x++) {
-        dst[x] = SkPackARGB32NoCheck(0xFF, src[x], src[x], src[x]);
+        dst[x] = SkPackARGB32NoCheck(0xFF, *src, *src, *src);
+        src += deltaSrc;
     }
     return SkSwizzler::kOpaque_ResultAlpha;
 }
 
 static SkSwizzler::ResultAlpha swizzle_gray_to_gray(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
-    memcpy(dstRow, src, width);
+        int deltaSrc, int y, const SkPMColor ctable[]) {
+
+    uint8_t* SK_RESTRICT dst = (uint8_t*) dstRow;
+    if (1 == deltaSrc) {
+        memcpy(dstRow, src, width);
+    } else {
+        for (int x = 0; x < width; x++) {
+            dst[x] = src[0];
+            src += deltaSrc;
+        }
+    }
     return SkSwizzler::kOpaque_ResultAlpha;
 }
 
 // kBGRX
 
 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[]) {
+        int deltaSrc, 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;
+        src += deltaSrc;
     }
     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[]) {
+        int deltaSrc, 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];
         UPDATE_RESULT_ALPHA(alpha);
         dst[x] = SkPackARGB32NoCheck(alpha, src[2], src[1], src[0]);
-        src += bytesPerPixel;
+        src += deltaSrc;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 static SkSwizzler::ResultAlpha swizzle_bgra_to_n32_premul(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+        int deltaSrc, 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];
         UPDATE_RESULT_ALPHA(alpha);
         dst[x] = SkPreMultiplyARGB(alpha, src[2], src[1], src[0]);
-        src += bytesPerPixel;
+        src += deltaSrc;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 // n32
 static SkSwizzler::ResultAlpha swizzle_rgbx_to_n32(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+        int deltaSrc, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     for (int x = 0; x < width; x++) {
         dst[x] = SkPackARGB32(0xFF, src[0], src[1], src[2]);
-        src += bytesPerPixel;
+        src += deltaSrc;
     }
     return SkSwizzler::kOpaque_ResultAlpha;
 }
 
 static SkSwizzler::ResultAlpha swizzle_rgba_to_n32_premul(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+        int deltaSrc, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
         unsigned alpha = src[3];
         UPDATE_RESULT_ALPHA(alpha);
         dst[x] = SkPreMultiplyARGB(alpha, src[0], src[1], src[2]);
-        src += bytesPerPixel;
+        src += deltaSrc;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 static SkSwizzler::ResultAlpha swizzle_rgba_to_n32_unpremul(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+        int deltaSrc, int y, const SkPMColor ctable[]) {
 
     uint32_t* SK_RESTRICT dst = reinterpret_cast<uint32_t*>(dstRow);
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
         unsigned alpha = src[3];
         UPDATE_RESULT_ALPHA(alpha);
         dst[x] = SkPackARGB32NoCheck(alpha, src[0], src[1], src[2]);
-        src += bytesPerPixel;
+        src += deltaSrc;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
 static SkSwizzler::ResultAlpha swizzle_rgba_to_n32_premul_skipZ(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int width,
-        int bytesPerPixel, int y, const SkPMColor ctable[]) {
+        int deltaSrc, int y, const SkPMColor ctable[]) {
 
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     INIT_RESULT_ALPHA;
     for (int x = 0; x < width; x++) {
         unsigned alpha = src[3];
         UPDATE_RESULT_ALPHA(alpha);
         if (0 != alpha) {
             dst[x] = SkPreMultiplyARGB(alpha, src[0], src[1], src[2]);
         }
-        src += bytesPerPixel;
+        src += deltaSrc;
     }
     return COMPUTE_RESULT_ALPHA;
 }
 
+// returns a sample size based on the input src and dst dimensions
+// can only down sample, so dstDimension must be <= than srcDimension
+static int get_sample_size(int srcDimension, int dstDimension) {

[scroggo, 2015/07/30 18:05:57]

Can this be shared with the other function that looks like this?

[emmaleer, 2015/07/30 22:27:56]

Yes, it now calls the function in SkScaledCodec.h
Currently it is a public function, but I remember you saying that we didn't want
it to be public?
Why not? I don't see any harm of it being public, since it doesn't change any
variables. 
I could change it to private, and make SkScaledCodec and SkSwizzler friend
classes. Would that be better? (if so, why would that be better)

[scroggo, 2015/07/31 13:35:33]

I just meant that it should not be a part of the public API - i.e. not in
include/ (not on SkCodec). You've made it a public function on SkScaledCodec,
which is in src/codec, which I think is appropriate.
No, friend classes should be used sparingly.

[emmaleer, 2015/07/31 18:41:56]

Acknowledged.

+    SkASSERT(dstDimension <= srcDimension);
+    return srcDimension / dstDimension;
+}
+
 /**
     FIXME: This was my idea to cheat in order to continue taking advantage of skipping zeroes.
     This would be fine for drawing normally, but not for drawing with transfer modes. Being
     honest means we can draw correctly with transfer modes, with the cost of not being able
     to take advantage of Android's free unwritten pages. Something to keep in mind when we
     decide whether to switch to unpremul default.
 static bool swizzle_rgba_to_n32_unpremul_skipZ(void* SK_RESTRICT dstRow,
                                                const uint8_t* SK_RESTRICT src,
                                                int width, int bitsPerPixel,
                                                const SkPMColor[]) {
     SkPMColor* SK_RESTRICT dst = (SkPMColor*)dstRow;
     unsigned alphaMask = 0xFF;
     for (int x = 0; x < width; x++) {
         unsigned alpha = src[3];
         // NOTE: We cheat here. The caller requested unpremul and skip zeroes. It's possible
         // the color components are not zero, but we skip them anyway, meaning they'll remain
         // zero (implied by the request to skip zeroes).
         if (0 != alpha) {
             dst[x] = SkPackARGB32NoCheck(alpha, src[0], src[1], src[2]);
         }
         src += deltaSrc;
         alphaMask &= alpha;
     }
     return alphaMask != 0xFF;
 }
 */
 
 SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc,
                                        const SkPMColor* ctable,
-                                       const SkImageInfo& info, void* dst,
+                                       const SkImageInfo& dstInfo, void* dst,
                                        size_t dstRowBytes,
-                                       SkCodec::ZeroInitialized zeroInit) {
-    if (info.colorType() == kUnknown_SkColorType || kUnknown == sc) {
+                                       SkCodec::ZeroInitialized zeroInit, 
+                                       const SkImageInfo& srcInfo) {
+    if (dstInfo.colorType() == kUnknown_SkColorType || kUnknown == sc) {
         return NULL;
     }
-    if (info.minRowBytes() > dstRowBytes) {
+    if (dstInfo.minRowBytes() > dstRowBytes) {
         return  NULL;
     }
     if ((kIndex == sc || kIndex4 == sc || kIndex2 == sc || kIndex1 == sc)
             && NULL == ctable) {
         return NULL;
     }
+
     RowProc proc = NULL;
+
     switch (sc) {
         case kIndex1:
         case kIndex2:
         case kIndex4:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_small_index_to_n32;
                     break;
                 case kIndex_8_SkColorType:
                     proc = &swizzle_small_index_to_index;
                     break;
                 default:
                     break;
             }
             break;
         case kIndex:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
                     // We assume the color premultiplied ctable (or not) as desired.
                     if (SkCodec::kYes_ZeroInitialized == zeroInit) {
                         proc = &swizzle_index_to_n32_skipZ;
                         break;
                     } else {
                         proc = &swizzle_index_to_n32;
                         break;
                     }
                     break;
                 case kIndex_8_SkColorType:
                     proc = &swizzle_index_to_index;
                     break;
                 default:
                     break;
             }
             break;
         case kGray:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_gray_to_n32;
                     break;
                 case kGray_8_SkColorType:
                     proc = &swizzle_gray_to_gray;
                 default:
                     break;
             }
             break;
         case kBGR:
         case kBGRX:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_bgrx_to_n32;
                     break;
                 default:
                     break;
             }
             break;
         case kBGRA:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
-                    switch (info.alphaType()) {
+                    switch (dstInfo.alphaType()) {
                         case kUnpremul_SkAlphaType:
                             proc = &swizzle_bgra_to_n32_unpremul;
                             break;
                         case kPremul_SkAlphaType:
                             proc = &swizzle_bgra_to_n32_premul;
                             break;
                         default:
                             break;
                     }
                     break;
                 default:
                     break;
             }
             break;
         case kRGBX:
             // TODO: Support other swizzles.
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_rgbx_to_n32;
                     break;
                 default:
                     break;
             }
             break;
         case kRGBA:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
-                    if (info.alphaType() == kUnpremul_SkAlphaType) {
+                    if (dstInfo.alphaType() == kUnpremul_SkAlphaType) {
                         // Respect zeroInit?
                         proc = &swizzle_rgba_to_n32_unpremul;
                     } else {
                         if (SkCodec::kYes_ZeroInitialized == zeroInit) {
                             proc = &swizzle_rgba_to_n32_premul_skipZ;
                         } else {
                             proc = &swizzle_rgba_to_n32_premul;
                         }
                     }
                     break;
                 default:
                     break;
             }
             break;
         case kRGB:
-            switch (info.colorType()) {
+            switch (dstInfo.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_rgbx_to_n32;
                     break;
                 default:
                     break;
             }
             break;
+        case kRGB_565:
+            switch (dstInfo.colorType()) {
+                case kRGB_565_SkColorType:
+                    proc = &sample;
+                    break;
+                default:
+                    break;
+            }
         default:
             break;
     }
     if (NULL == proc) {
         return NULL;
     }
 
     // Store deltaSrc in bytes if it is an even multiple, otherwise use bits
     int deltaSrc = SkIsAlign8(BitsPerPixel(sc)) ? BytesPerPixel(sc) :
             BitsPerPixel(sc);
-    return SkNEW_ARGS(SkSwizzler, (proc, ctable, deltaSrc, info, dst,
-                                   dstRowBytes));
+
+    int sampleX = get_sample_size(srcInfo.width(), dstInfo.width());

[scroggo, 2015/07/30 18:05:57]

It seems a little weird that we pass the full image info, when all we need is
the width.

[emmaleer, 2015/07/30 22:27:56]

Right. I've changed this to only pass the width. 

+    
+    return SkNEW_ARGS(SkSwizzler, (proc, ctable, deltaSrc, dstInfo, dst,
+                                   dstRowBytes, sampleX));
 }
 
 SkSwizzler::SkSwizzler(RowProc proc, const SkPMColor* ctable,
                        int deltaSrc, const SkImageInfo& info, void* dst,
-                       size_t rowBytes)
+                       size_t rowBytes, int sampleX)
     : fRowProc(proc)
     , fColorTable(ctable)
     , fDeltaSrc(deltaSrc)
     , fDstInfo(info)
     , fDstRow(dst)
     , fDstRowBytes(rowBytes)
     , fCurrY(0)
+    , fSampleX(sampleX)
+    , fX0(sampleX == 1 ? 0 : sampleX >> 1)
 {
+    // check that fX0 is less than original width
+    SkASSERT(fX0 >= 0 && fX0 < fDstInfo.width() * fSampleX);
     SkDEBUGCODE(fNextMode = kUninitialized_NextMode);
 }
 
 SkSwizzler::ResultAlpha SkSwizzler::next(const uint8_t* SK_RESTRICT src) {
     SkASSERT(0 <= fCurrY && fCurrY < fDstInfo.height());
     SkASSERT(fDstRow != NULL);
     SkASSERT(kDesignateRow_NextMode != fNextMode);
     SkDEBUGCODE(fNextMode = kConsecutive_NextMode);
 
     // Decode a row
-    const ResultAlpha result = fRowProc(fDstRow, src, fDstInfo.width(),
-            fDeltaSrc, fCurrY, fColorTable);
+    const ResultAlpha result = fRowProc(fDstRow, src + fX0 * fDeltaSrc, fDstInfo.width(),
+            fSampleX * fDeltaSrc, fCurrY, fColorTable);
 
     // Move to the next row and return the result
     fCurrY++;
     fDstRow = SkTAddOffset<void>(fDstRow, fDstRowBytes);
     return result;
 }
 
 SkSwizzler::ResultAlpha SkSwizzler::next(const uint8_t* SK_RESTRICT src,
         int y) {
     SkASSERT(0 <= y && y < fDstInfo.height());
     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,
+    return fRowProc(row, src + fX0 * fDeltaSrc, fDstInfo.width(), fSampleX * fDeltaSrc, fCurrY,
             fColorTable);
 }
 
 void SkSwizzler::Fill(void* dstStartRow, const SkImageInfo& dstInfo, size_t dstRowBytes,
         uint32_t numRows, uint32_t colorOrIndex, const SkPMColor* colorTable) {
     SkASSERT(dstStartRow != NULL);
     SkASSERT(numRows <= (uint32_t) dstInfo.height());
 
     // Calculate bytes to fill.  We use getSafeSize since the last row may not be padded.
     const size_t bytesToFill = dstInfo.makeWH(dstInfo.width(), numRows).getSafeSize(dstRowBytes);
@@ skipping 40 matching lines @@
             // bits of SK_ColorBLACK are identical to the grayscale representation
             // for black. 
             memset(dstStartRow, (uint8_t) colorOrIndex, bytesToFill);
             break;
         default:
             SkCodecPrintf("Error: Unsupported dst color type for fill().  Doing nothing.\n");
             SkASSERT(false);
             break;
     }
 }