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,

[scroggo, 2015/07/30 17:53:01]

Could you add a description?

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

Yes.
Also, we can use the sample function for all jpeg images.
I haven't found a nice way to do that yet, or if that is even possible.

+                                      int width, int deltaSrc, int y, const SkPMColor ctable[]){
+    uint8_t* SK_RESTRICT dst = (uint8_t*) dstRow;

[scroggo, 2015/07/30 17:53:01]

Does this do what we want it to? It looks like it is used to sample 565, but it
works in 1-byte increments. It seems like this would not line up with the actual
pixels?

I think you would need a different version for different colortypes.

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

I think this is working somehow..
When I test it, deltaSrc is 16 (so I guess deltaSrc is in bits sometimes and not
bytes)
So each time 16 bits is added to src.
I'm not exactly sure how the src pointer knows to add bits and not bytes
though.. 
Usually when you add 1 to a pointer it adds 1 byte right?
The images looks correct when I run dm.

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

That is correct. For the "small index" versions (all BMP, I believe), it will be
in bits.
When you add 1 to a pointer it will add the size of the pointer.

If you have a uint32_t*, adding one will move to the next uint32_t, meaning it
will add four bytes. (On a related note, you cannot add to a void*, where it is
not clear what you would add.)

Adding one to a uint8_t*, as you are doing here, will add one byte. So if
deltaSrc is 16, you'll move 16 bytes forward.

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

I've fixed this to work with 565

+    for (int x = 0; x < width; x++) {
+        dst[x] = src[0];
+        src += deltaSrc;
+    }

[scroggo, 2015/07/30 17:53:01]

This method should return a value.

For 565, we do not need to check anything (it is always opaque), so you can just
return a max alpha of 0xFF. (Matt will have to remind me what zeroAlpha is.)

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

Acknowledged.

+}
 // 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;
 }
 
 /**
     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.
@@ skipping 15 matching lines @@
         alphaMask &= alpha;
     }
     return alphaMask != 0xFF;
 }
 */
 
 SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc,
                                        const SkPMColor* ctable,
                                        const SkImageInfo& info, void* dst,
                                        size_t dstRowBytes,
-                                       SkCodec::ZeroInitialized zeroInit) {
+                                       SkCodec::ZeroInitialized zeroInit, int sampleX) {
     if (info.colorType() == kUnknown_SkColorType || kUnknown == sc) {
         return NULL;
     }
     if (info.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()) {
                 case kN32_SkColorType:
                     proc = &swizzle_small_index_to_n32;
                     break;
                 case kIndex_8_SkColorType:
                     proc = &swizzle_small_index_to_index;
@@ skipping 90 matching lines @@
             break;
         case kRGB:
             switch (info.colorType()) {
                 case kN32_SkColorType:
                     proc = &swizzle_rgbx_to_n32;
                     break;
                 default:
                     break;
             }
             break;
+        case kRGB_565:
+            switch (info.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));
+                                   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(),

[msarett, 2015/07/30 13:55:38]

nit: extra space before src

[emmaleer, 2015/07/30 17:50:39]

Acknowledged.

+            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 34 matching lines @@
             break;
         case kGray_8_SkColorType:
             // If the destination is kGray, the caller passes in an 8-bit color.
             // We will not assert that the high bits of colorOrIndex must be zeroed.
             // This allows us to take advantage of the fact that the low 8 bits of an
             // SKPMColor may be a valid a grayscale color.  For example, the low 8
             // bits of SK_ColorBLACK are identical to the grayscale representation
             // for black. 
             memset(dstStartRow, (uint8_t) colorOrIndex, bytesToFill);
             break;
+

[msarett, 2015/07/30 13:55:38]

nit: extra new line

Also, you might want to try rebasing.  I have updated this function to fix the
bug you caught :).  As long as this new line isn't here I don't think there
should be a merge conflict.

[emmaleer, 2015/07/30 17:50:39]

Acknowledged.

[scroggo, 2015/07/30 17:53:01]

Just as a general piece of advice, I find it useful to rebase and upload without
other changes; otherwise when looking at the difference between two revisions
it's unclear which changes you introduced vs someone else introduced.

         default:
             SkCodecPrintf("Error: Unsupported dst color type for fill().  Doing nothing.\n");
             SkASSERT(false);
             break;
     }
 }