PDF: Add (low-memory) SkPDFBitmap class

src/pdf/SkPDFBitmap.cpp

Index: src/pdf/SkPDFBitmap.cpp
diff --git a/src/pdf/SkPDFBitmap.cpp b/src/pdf/SkPDFBitmap.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..5f0dcec27cb7c492b103e359a57f57b0205c58e3
--- /dev/null
+++ b/src/pdf/SkPDFBitmap.cpp
@@ -0,0 +1,173 @@
+/*
+ * 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 "SkPDFBitmap.h"
+#include "SkPDFCanon.h"
+#include "SkUnPreMultiply.h"
+#include "SkColorPriv.h"
+#include "SkStream.h"
+#include "SkDeflateWStream.h"
+#include "SkFlate.h"
+
+static void emit_pdf_bitmap_dict(SkWStream* stream,
+                                 SkPDFCatalog* catalog,
+                                 SkISize dimensions,
+                                 int32_t length,
+                                 SkPDFObject* smask,
+                                 bool deflate,
+                                 const char colorSpace[]) {
+    SkPDFDict pdfDict("Xobject");
+    pdfDict.insertName("Subtype", "Image");
+    pdfDict.insertInt("Width", dimensions.width());
+    pdfDict.insertInt("Height", dimensions.height());
+    pdfDict.insertName("ColorSpace", colorSpace);
+    pdfDict.insertInt("BitsPerComponent", 8);
+    if (smask) {
+        pdfDict.insert("SMask", new SkPDFObjRef(smask))->unref();
+    }
+    pdfDict.insertInt("Length", length);
+    if (deflate) {
+        pdfDict.insertName("Filter", "FlateDecode");
+    }
+    pdfDict.emitObject(stream, catalog);
+}
+
+static void pmcolor_scanline_to_rgb24(const SkPMColor* src,

[mtklein, 2015/02/12 00:21:46]

This is just a suggestion.  I've grown to like (dst, src, count) argument order
for these types of functions, to stay consistent with memcpy, memset, etc.

[hal.canary, 2015/02/12 21:28:03]

Refactored out.

+                                      uint8_t* dst, int width) {
+    for (int x = 0; x < width; ++x) {
+        const SkPMColor pmColor = *src++;
+        const uint32_t s = SkUnPreMultiply::GetScale(SkGetPackedA32(pmColor));
+        *dst++ = SkUnPreMultiply::ApplyScale(s, SkGetPackedR32(pmColor));
+        *dst++ = SkUnPreMultiply::ApplyScale(s, SkGetPackedG32(pmColor));
+        *dst++ = SkUnPreMultiply::ApplyScale(s, SkGetPackedB32(pmColor));
+    }
+}
+
+static void pmcolor_alpha_scanline_to_a8(const SkPMColor* src,
+                                         uint8_t* dst, int width) {
+    for (int x = 0; x < width; ++x) {
+        *dst++ = SkGetPackedA32(*src++);
+    }
+}
+
+SkPDFBitmap::~SkPDFBitmap() {
+    if (!fIsAlpha) {

[mtklein, 2015/02/12 00:21:46]

It'd be nice to explain fIsAlpha and why we track it.  Reading linearly up to
here I just slammed into confusion wondering what fIsAlpha is and why it
matters.

[hal.canary, 2015/02/12 21:28:03]

Done.

+        SkAutoMutexAcquire autoMutexAcquire(SkPDFCanon::GetBitmapMutex());
+        SkPDFCanon::GetCanon().removeBitmap(this);
+    }
+}
+
+void SkPDFBitmap::addResources(SkTSet<SkPDFObject*>* resourceSet,
+                               SkPDFCatalog* catalog) const {
+    if (fSMask.get()) {
+        resourceSet->add(fSMask.get());
+    }
+}
+
+void SkPDFBitmap::emitObject(SkWStream* stream, SkPDFCatalog* catalog) {
+    SkASSERT(kN32_SkColorType == fBitmap.colorType());
+    SkAutoLockPixels autoLockPixels(fBitmap);
+    SkASSERT(fBitmap.getPixels());
+
+    if (SkFlate::HaveFlate()) {
+        SkDynamicMemoryWStream buffer;
+        size_t scanlineLength = fIsAlpha ? fBitmap.width()
+                                         : 3 * fBitmap.width();
+        SkAutoTMalloc<uint8_t> scanline(scanlineLength);
+        if (fIsAlpha) {
+            SkDeflateWStream deflateWStream(&buffer);
+            for (int y = 0; y < fBitmap.height(); ++y) {
+                pmcolor_alpha_scanline_to_a8(fBitmap.getAddr32(0, y),
+                                             scanline.get(),
+                                             fBitmap.width());
+                deflateWStream.write(scanline.get(), scanlineLength);
+            }
+            // deflateWStream is deleted.

[mtklein, 2015/02/12 00:21:46]

Is this salient here but not in the rgb case?

[hal.canary, 2015/02/12 21:28:03]

refactored out

+        } else {
+            SkDeflateWStream deflateWStream(&buffer);
+            for (int y = 0; y < fBitmap.height(); ++y) {
+                pmcolor_scanline_to_rgb24(fBitmap.getAddr32(0, y),
+                                          scanline.get(),
+                                          fBitmap.width());
+                deflateWStream.write(scanline.get(), scanlineLength);
+            }
+        }
+        SkAutoTDelete<SkStreamAsset> asset(buffer.detachAsStream());
+        emit_pdf_bitmap_dict(stream,
+                             catalog,
+                             fBitmap.dimensions(),
+                             asset->getLength(),
+                             fSMask,
+                             true,

[mtklein, 2015/02/12 00:21:46]

Is this /* using DEFLATE */ and false /* not compressed */ ?

+                             fIsAlpha ? "DeviceGray" : "DeviceRGB");
+        stream->writeText(" stream\n");
+        stream->writeStream(asset.get(), asset->getLength());
+        stream->writeText("\nendstream");
+        return;
+    } else {  // !SkFlate::HaveFlate()
+        size_t scanlineLength = fIsAlpha ? fBitmap.width()

[mtklein, 2015/02/12 00:21:46]

Seems like an awful lot of code duplicated between the flate and non flate
paths.  Think you can factor it out?

+                                         : 3 * fBitmap.width();
+        emit_pdf_bitmap_dict(stream,
+                             catalog,
+                             fBitmap.dimensions(),
+                             fBitmap.height() * scanlineLength,
+                             fSMask,
+                             false,
+                             fIsAlpha ? "DeviceGray" : "DeviceRGB");
+        stream->writeText(" stream\n");
+
+        SkAutoTMalloc<uint8_t> scanline(scanlineLength);
+
+        if (fIsAlpha) {
+            for (int y = 0; y < fBitmap.height(); ++y) {
+                pmcolor_alpha_scanline_to_a8(fBitmap.getAddr32(0, y),
+                                             scanline.get(),
+                                             fBitmap.width());
+                stream->write(scanline.get(), scanlineLength);
+            }
+        } else {
+            for (int y = 0; y < fBitmap.height(); ++y) {
+                pmcolor_scanline_to_rgb24(fBitmap.getAddr32(0, y),
+                                          scanline.get(),
+                                          fBitmap.width());
+                stream->write(scanline.get(), scanlineLength);
+            }
+        }
+        stream->writeText("\nendstream");
+        return;
+    }
+}
+
+SkPDFBitmap::SkPDFBitmap(const SkBitmap& bm, bool isAlpha, SkPDFBitmap* smask)
+    : fBitmap(bm), fSMask(smask), fIsAlpha(isAlpha) {}
+
+SkPDFBitmap* SkPDFBitmap::Create(const SkBitmap& bitmap,
+                                 const SkIRect& subset) {
+    if (kN32_SkColorType != bitmap.colorType()) {
+        return NULL;
+    }
+    SkBitmap bm;
+    if (!bitmap.extractSubset(&bm, subset)) {
+        return NULL;
+    }
+    if (bm.drawsNothing()) {
+        return NULL;

[mtklein, 2015/02/12 00:21:46]

Is this really an error?

[hal.canary, 2015/02/12 21:28:03]

Just a shortcut.

+    }
+    SkAutoMutexAcquire autoMutexAcquire(SkPDFCanon::GetBitmapMutex());
+    SkPDFCanon& canon = SkPDFCanon::GetCanon();
+    SkPDFBitmap* pdfBitmap = canon.findBitmap(bm);
+    if (pdfBitmap) {
+        return SkRef(pdfBitmap);
+    }  // src/pdf/SkPDFBitmap.cpp
+    SkPDFBitmap* smask = NULL;
+    if (!bitmap.isOpaque() && !SkBitmap::ComputeIsOpaque(bitmap)) {
+        smask = SkNEW_ARGS(SkPDFBitmap, (bm, true, NULL));

[mtklein, 2015/02/12 00:21:46]

Are the smasks always alpha-only and the main SkPDFBitmaps always not?  If so,
you might want to cleave them apart into two different classes.

[hal.canary, 2015/02/12 21:28:03]

Okay, done.  Seems like more code this way.

+    }
+    pdfBitmap = SkNEW_ARGS(SkPDFBitmap, (bm, false, smask));
+    canon.addBitmap(pdfBitmap);
+    return pdfBitmap;
+}