genesys: Add a way to use an image as a source for a pipeline

backend/genesys_image_pipeline.cc

@@ -113,6 +113,19 @@ void ImagePipelineNodeArraySource::get_next_row_data(std::uint8_t* out_data)
 }
 
 
+ImagePipelineNodeImageSource::ImagePipelineNodeImageSource(const Image& source) :
+    source_{source}
+{}
+
+void ImagePipelineNodeImageSource::get_next_row_data(std::uint8_t* out_data)
+{
+    if (next_row_ >= get_height()) {
+        throw SaneException("Trying to access line that is out of bounds");
+    }
+    std::memcpy(out_data, source_.get_row_ptr(next_row_), get_row_bytes());
+    next_row_++;
+}
+
 void ImagePipelineNodeFormatConvert::get_next_row_data(std::uint8_t* out_data)
 {
     auto src_format = source_.get_format();

backend/genesys_image_pipeline.h

@@ -44,6 +44,7 @@
 #ifndef BACKEND_GENESYS_IMAGE_PIPELINE_H
 #define BACKEND_GENESYS_IMAGE_PIPELINE_H
 
+#include "genesys_image.h"
 #include "genesys_image_pixel.h"
 #include "genesys_image_buffer.h"
 
@@ -178,6 +179,23 @@ private:
 };
 
 
+/// A pipeline node that produces data from the given image
+class ImagePipelineNodeImageSource : public ImagePipelineNode
+{
+public:
+    ImagePipelineNodeImageSource(const Image& source);
+
+    std::size_t get_width() const override { return source_.get_width(); }
+    std::size_t get_height() const override { return source_.get_height(); }
+    PixelFormat get_format() const override { return source_.get_format(); }
+
+    void get_next_row_data(std::uint8_t* out_data) override;
+
+private:
+    const Image& source_;
+    std::size_t next_row_ = 0;
+};
+
 // A pipeline node that converts between pixel formats
 class ImagePipelineNodeFormatConvert : public ImagePipelineNode
 {