Add subsetting to SkScaledCodec

src/codec/SkCodec.cpp

Index: src/codec/SkCodec.cpp
diff --git a/src/codec/SkCodec.cpp b/src/codec/SkCodec.cpp
index 917df317fb3552e4ee72b005693c340fbfa9dcf6..64b2ad6602880454953b68ee10374ab0334587e9 100644
--- a/src/codec/SkCodec.cpp
+++ b/src/codec/SkCodec.cpp
@@ -111,6 +111,59 @@ bool SkCodec::rewindIfNeeded() {
     return this->onRewind();
 }
 
+SkISize SkCodec::getScaledDimensions(float desiredScale) const {
+    // Negative and zero scales are errors.
+    SkASSERT(desiredScale > 0.0f);
+    if (desiredScale <= 0.0f) {
+        return SkISize::Make(0, 0);
+    }
+
+    // Upscaling is not supported. Return the original size if the client
+    // requests an upscale.
+    if (desiredScale >= 1.0f) {
+        return this->getInfo().dimensions();
+    }
+    return this->onGetScaledDimensions(desiredScale);
+}
+
+bool SkCodec::getValidSubset(SkIRect* desiredSubset) const {
+    if (!desiredSubset) {
+        return false;
+    }
+
+    if (!is_valid_subset(desiredSubset, this->getInfo().dimensions())) {
+        return false;
+    }
+
+    return this->onGetValidSubset(desiredSubset);
+}
+
+bool SkCodec::getScaledSubsetDimensions(float desiredScale, Options* options) const {
+    // Negative and zero scales are errors.
+    SkASSERT(desiredScale > 0.0f);
+    if (desiredScale <= 0.0f) {
+        return false;
+    }
+
+    // Upscaling is not supported. We will suggest a full decode if
+    // upscaling is requested.
+    if (desiredScale >= 1.0f) {
+        desiredScale = 1.0f;
+    }
+
+    // If the client is not requesting a subset decode,
+    // getScaledDimensions() should be used.
+    if (nullptr == options->fSubset) {
+        return false;
+    }
+
+    if (!is_valid_subset(options->fSubset, this->getInfo().dimensions())) {
+        return false;
+    }
+
+    return this->onGetScaledSubsetDimensions(desiredScale, options);
+}
+
 SkCodec::Result SkCodec::getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
                                    const Options* options, SkPMColor ctable[], int* ctableCount) {
     if (kUnknown_SkColorType == info.colorType()) {
@@ -195,9 +248,17 @@ SkCodec::Result SkCodec::getPixels(const SkImageInfo& info, void* pixels, size_t
 }
 
 SkCodec::Result SkCodec::startScanlineDecode(const SkImageInfo& dstInfo,
-        const SkCodec::Options* options, SkPMColor ctable[], int* ctableCount) {
+        const SkCodec::Options* options, SkPMColor ctable[], int* ctableCount, int subsetLeft,
+        int subsetWidth) {
     // Reset fCurrScanline in case of failure.
     fCurrScanline = -1;
+
+    // Ensure that the subset parameters are valid
+    if (0 > subsetLeft || subsetLeft >= dstInfo.width() || 0 > subsetWidth ||
+            subsetLeft + subsetWidth > dstInfo.width()) {
+        return kInvalidParameters;
+    }
+
     // Ensure that valid color ptrs are passed in for kIndex8 color type
     if (kIndex_8_SkColorType == dstInfo.colorType()) {
         if (nullptr == ctable || nullptr == ctableCount) {
@@ -233,7 +294,8 @@ SkCodec::Result SkCodec::startScanlineDecode(const SkImageInfo& dstInfo,
         return kInvalidScale;
     }
 
-    const Result result = this->onStartScanlineDecode(dstInfo, *options, ctable, ctableCount);
+    const Result result = this->onStartScanlineDecode(dstInfo, *options, ctable, ctableCount,
+            subsetLeft, subsetWidth);
     if (result != SkCodec::kSuccess) {
         return result;
     }
@@ -244,8 +306,13 @@ SkCodec::Result SkCodec::startScanlineDecode(const SkImageInfo& dstInfo,
     return kSuccess;
 }
 
+SkCodec::Result SkCodec::startScanlineDecode(const SkImageInfo& dstInfo,
+        const SkCodec::Options* options, SkPMColor ctable[], int* ctableCount) {
+    return this->startScanlineDecode(dstInfo, options, ctable, ctableCount, 0, dstInfo.width());
+}
+
 SkCodec::Result SkCodec::startScanlineDecode(const SkImageInfo& dstInfo) {
-    return this->startScanlineDecode(dstInfo, nullptr, nullptr, nullptr);
+    return this->startScanlineDecode(dstInfo, nullptr, nullptr, nullptr, 0, dstInfo.width());
 }
 
 int SkCodec::getScanlines(void* dst, int countLines, size_t rowBytes) {