Added waveform functions

src/waveform.cpp

@@ -0,0 +1,115 @@
+#include "waveform.hpp"
+
+
+/*
+Given an input_buffer, create a waveform of size width, height.
+
+@param input_buffer Buffer to read from.
+@param output Where to place output. Will be overwritten.
+@param width Width of waveform. This is how many values will be written to output.
+@param height Height of waveform. Every value in the output vector is less than or equal to height.
+*/
+void waveform_generate(
+	const Buffer& input_buffer,
+	std::vector<size_t>& output,
+	size_t width,
+	size_t height
+) {
+	const int samples_per_column = input_buffer.get_output().size() / width;
+
+	if (samples_per_column == 0) {
+		printf("Too few samples %d\n", (int) input_buffer.get_output().size());
+		return;
+	}
+
+	double bar_height;
+	for (size_t x = 0; x < width; x++) {
+		bar_height = 0;
+
+		// Average bins
+		for (int j = 0; j < samples_per_column; j++) {
+			bar_height += input_buffer.get_output()[x*samples_per_column+j] + INT16_MAX;
+		}
+		bar_height /= samples_per_column;
+
+		// Scale bar height
+		bar_height *= height / (double) UINT16_MAX;
+
+		output[x] = (size_t) bar_height;
+	}
+}
+
+
+
+/*
+Draw a waveform in a bitmap.
+
+@param waveform Waveform data, as generated by gen_waveform
+@param bitmap Bitmap to draw to. This will be modified, but will NOT be cleared.
+*/
+void waveform_draw_bitmap(
+	const std::vector<size_t>& waveform,
+	Bitmap& bitmap
+) {
+	size_t pt = 0;
+	size_t prev_pt = 0;
+	size_t delta;
+	for (size_t x = 0; x < waveform.size(); x++) {
+		prev_pt = pt;
+		pt = waveform[x];
+
+		bitmap.setpixel(
+			pt, x,
+			0xFF, 0x00, 0x00
+		);
+
+		// If the gap between two consecutive points is too big,
+		// intermediate values are needed for the wave to be watchable.
+		delta = pt>prev_pt ? pt-prev_pt : prev_pt-pt;
+		if ( (x > 0) && (delta > 1) ){
+			const size_t half = (prev_pt + pt) / 2;
+
+			if (prev_pt < pt) {
+				for (auto y = prev_pt; y < pt; y++) {
+					bitmap.setpixel(
+						y, x - (y < half),
+						0xFF, 0x00, 0x00
+					);
+				}
+			} else {
+				for (auto y = prev_pt; y > pt; y--) {
+					bitmap.setpixel(
+						y, x - (y > half),
+						0xFF, 0x00, 0x00
+					);
+				}
+			}
+		}
+	}
+}
+
+
+/*
+Example:
+
+int main(int argc, char *argv[]) {
+	Buffer buf = Buffer(
+		"/tmp/mpd.fifo",
+		44100 / 2, // Keep 500ms of data in buffer
+		(44100 / 60 * 10)
+		// Double both if stereo
+	);
+
+	Bitmap b = Bitmap(width, 100);
+	std::vector<size_t> waveform;
+	waveform.resize(width);
+
+	while(1) {
+		b.clear();
+		buf.update();
+		waveform_generate(buf, waveform, width, 100);
+		waveform_draw_bitmap(waveform, b);
+		b.save("/tmp/o.bmp");
+	}
+}
+*/

src/waveform.hpp

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stdio.h>
+#include <cstdint>
+#include <vector>
+
+#include "bitmap/bitmap.hpp"
+#include "buffer/buffer.hpp"
+
+
+void waveform_generate(
+	const Buffer &input_buffer,
+	std::vector<size_t>& output,
+	size_t width,
+	size_t height
+);
+
+
+void waveform_draw_bitmap(
+	const std::vector<size_t>& waveform,
+	Bitmap& bitmap
+);