Multiple crops

src/libpisp/backend/tiling/crop_stage.cpp

@@ -13,7 +13,7 @@
 using namespace tiling;
 
 CropStage::CropStage(char const *name, Stage *upstream, Config const &config, int struct_offset)
-	: BasicStage(name, upstream->GetPipeline(), upstream, struct_offset), config_(config)
+	: BasicStage(name, upstream->GetPipeline(), upstream, struct_offset), config_(config), started_(false)
 {
 }
 
@@ -27,6 +27,11 @@ void CropStage::PushStartUp(int output_start, Dir dir)
 	PISP_LOG(debug, "(" << name_ << ") Enter with output_start " << output_start);
 
 	int input_start = output_start + config_.crop[dir].offset;
+	// input_start can never be negative here, but it is possible to have output_start
+	// negative if, for example, a branch starts producing output on the second
+	// tile in a row (or column) and the resampler requires left (or top) context pixels.
+	if (input_start < 0)
+		throw std::runtime_error("input start is negative: " + std::to_string(input_start));
 	output_interval_.offset = output_start;
 	input_interval_.offset = input_start;
 
@@ -39,6 +44,17 @@ int CropStage::PushEndDown(int input_end, Dir dir)
 	PISP_LOG(debug, "(" << name_ << ") Enter with input_end " << input_end);
 
 	int output_end = input_end - config_.crop[dir].offset;
+
+	// If negative, no output will be generated for this tile. Terminate the
+	// iteration here and don't go futher downstream.
+	if (output_end < 0)
+	{
+		PISP_LOG(debug, "(" << name_ << ") Output branch not started, terminating ");
+		return 0;
+	}
+
+	started_ = true;
+
 	if (output_end > config_.crop[dir].length)
 		output_end = config_.crop[dir].length;
 	input_interval_.SetEnd(input_end);
@@ -63,6 +79,15 @@ void CropStage::PushEndUp(int output_end, Dir dir)
 void CropStage::PushCropDown(Interval interval, Dir dir)
 {
 	PISP_LOG(debug, "(" << name_ << ") Enter with interval " << interval);
+
+	// Branch has not started producing output.  Terminate the iteration here
+	// and don't go futher downstream.
+	if (!started_)
+	{
+		PISP_LOG(debug, "(" << name_ << ") Output branch not started, terminating ");
+		return;
+	}
+
 	PISP_ASSERT(interval > input_interval_);
 
 	input_interval_ = interval;
@@ -72,3 +97,8 @@ void CropStage::PushCropDown(Interval interval, Dir dir)
 	PISP_LOG(debug, "(" << name_ << ") Exit with interval " << output_interval_);
 	downstream_->PushCropDown(output_interval_, dir);
 }
+
+void CropStage::Reset()
+{
+	started_ = false;
+}

src/libpisp/backend/tiling/crop_stage.hpp

@@ -25,9 +25,11 @@ class CropStage : public BasicStage
 	virtual int PushEndDown(int input_end, Dir dir);
 	virtual void PushEndUp(int output_end, Dir dir);
 	virtual void PushCropDown(Interval interval, Dir dir);
+	void Reset() override;
 
 private:
 	Config config_;
+	bool started_;
 };
 
 } // namespace tiling

src/libpisp/backend/tiling/pipeline.cpp

@@ -16,7 +16,7 @@
 
 using namespace tiling;
 
-Pipeline::Pipeline(char const *name, Config const &config) : name_(name), config_(config)
+Pipeline::Pipeline(char const *name, Config const &config) : name_(name), config_(config), first_tile_(false)
 {
 }
 
@@ -74,6 +74,7 @@ int Pipeline::tileDirection(Dir dir, void *mem, size_t num_items, size_t item_si
 	reset();
 	bool done = false;
 	unsigned int num_tiles = 0;
+	first_tile_ = true;
 	for (; !done; num_tiles++)
 	{
 		PISP_LOG(debug, "----------------------------------------------------------------");
@@ -94,6 +95,7 @@ int Pipeline::tileDirection(Dir dir, void *mem, size_t num_items, size_t item_si
 		done = true;
 		for (auto s : outputs_)
 			done &= s->Done(dir);
+		first_tile_ = false;
 	}
 
 	PISP_LOG(debug, "Made " << num_tiles << " tiles in direction " << dir);

src/libpisp/backend/tiling/pipeline.hpp

@@ -37,6 +37,7 @@ class Pipeline
 	void AddInputStage(InputStage *input_stage);
 	void AddOutputStage(OutputStage *output_stage);
 	void Tile(void *mem, size_t num_items, size_t item_size, Length2 *grid);
+	bool FirstTile() const { return first_tile_; }
 
 private:
 	int tileDirection(Dir dir, void *mem, size_t num_items, size_t item_size);
@@ -46,6 +47,7 @@ class Pipeline
 	std::vector<Stage *> stages_;
 	std::vector<InputStage *> inputs_;
 	std::vector<OutputStage *> outputs_;
+	bool first_tile_;
 };
 
 } // namespace tiling

src/libpisp/backend/tiling/rescale_stage.cpp

@@ -34,8 +34,11 @@ void RescaleStage::PushStartUp(int output_start, Dir dir)
 	int input_start_P = output_start * config_.scale[dir];
 	int input_start = input_start_P >> config_.precision;
 	int input_start_w_context = input_start - config_.start_context[dir];
-
-	if (input_start_w_context < 0)
+	// input_start_w_context is allowed to go negative here if, for example, the branch starts producing output
+	// on the second tile in a row/column and the resampler requires left context pixels. In such cases, the left/top
+	// edge flag will not be set on the tile and the hardware cannot remove the left/top context pixels. So allow
+	// negative values on all but the left/top edge tile.
+	if (GetPipeline()->FirstTile() && input_start_w_context < 0)
 		input_start_w_context = 0;
 	output_interval_.offset = output_start;
 	input_interval_.offset = input_start_w_context;