Bodgy code to write PNG files the size of the LCD screen.

firmware/common/png_writer.cpp

@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2016 Jared Boone, ShareBrained Technology, Inc.
+ *
+ * This file is part of PortaPack.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "png_writer.hpp"
+
+static constexpr std::array<uint8_t, 8> png_file_header { {
+	0x89, 0x50, 0x4e, 0x47,
+	0x0d, 0x0a, 0x1a, 0x0a,
+} };
+
+static constexpr std::array<uint8_t, 25> png_ihdr_screen_capture { {
+	0x00, 0x00, 0x00, 0x0d,		// IHDR length
+	0x49, 0x48, 0x44, 0x52,		// IHDR type
+	0x00, 0x00, 0x00, 0xf0,		// width = 240
+	0x00, 0x00, 0x01, 0x40,		// height = 320
+	0x08,						// bit_depth = 8
+	0x02,						// color_type = 2
+	0x00,						// compression_method = 0
+	0x00,						// filter_method = 0
+	0x00,						// interlace_method = 0
+	0x0d, 0x8a, 0x66, 0x04,		// CRC
+} };
+
+static constexpr std::array<uint8_t, 4> png_idat_chunk_type { {
+	0x49, 0x44, 0x41, 0x54,		// IDAT type
+} };
+
+static constexpr std::array<uint8_t, 12> png_iend { {
+	0x00, 0x00, 0x00, 0x00,		// IEND length
+	0x49, 0x45, 0x4e, 0x44,		// IEND type
+	0xae, 0x42, 0x60, 0x82,		// CRC
+} };
+
+PNGWriter::PNGWriter(
+	const std::string& filename
+)
+{
+	file.open(filename);
+	file.write(png_file_header);
+	file.write(png_ihdr_screen_capture);
+	
+	write_chunk_header(
+		2 + height * (5 + 1 + width * 3) + 4,
+		png_idat_chunk_type
+	);
+
+	constexpr std::array<uint8_t, 2> zlib_header { 0x78, 0x01 };	// Zlib CM, CINFO, FLG.
+	write_chunk_content(zlib_header);
+}
+
+PNGWriter::~PNGWriter() {
+	write_chunk_content(adler_32.bytes());
+	write_chunk_crc();
+
+	file.write(png_iend);
+}
+
+void PNGWriter::write_scanline(const std::array<ui::ColorRGB888, 240>& scanline) {
+	constexpr uint8_t scanline_filter_type = 0;
+	constexpr uint32_t deflate_block_length = 1 + sizeof(scanline);
+
+	const std::array<uint8_t, 6> deflate_and_scanline_header {
+		(scanline_count == (height - 1)) ? 0x01 : 0x00,	// DEFLATE header bits, bfinal=0, btype=00
+		static_cast<uint8_t>((deflate_block_length >> 0) & 0xff),			// Length LSB
+		static_cast<uint8_t>((deflate_block_length >> 8) & 0xff),			// Length MSB
+		static_cast<uint8_t>((deflate_block_length >> 0) & 0xff) ^ 0xff,	// ~Length LSB
+		static_cast<uint8_t>((deflate_block_length >> 8) & 0xff) ^ 0xff,	// ~Length MSB
+		scanline_filter_type,
+	};
+	write_chunk_content(deflate_and_scanline_header);
+
+	adler_32.feed(scanline_filter_type);
+	adler_32.feed(scanline);
+
+	// Small writes to avoid some sort of large-transfer plus block
+	// boundary FatFs or SDC driver bug?
+	write_chunk_content(&scanline[  0], 80 * sizeof(ui::ColorRGB888));
+	write_chunk_content(&scanline[ 80], 80 * sizeof(ui::ColorRGB888));
+	write_chunk_content(&scanline[160], 80 * sizeof(ui::ColorRGB888));
+
+	scanline_count++;
+}
+
+void PNGWriter::write_chunk_header(
+	const size_t length,
+	const std::array<uint8_t, 4>& type
+) {
+	write_uint32_be(length);
+	crc.reset();
+	write_chunk_content(type);
+}
+
+void PNGWriter::write_chunk_content(const void* const p, const size_t count) {
+	file.write(p, count);
+	crc.process_bytes(p, count);
+}
+
+void PNGWriter::write_chunk_crc() {
+	write_uint32_be(crc.checksum());
+}
+
+void PNGWriter::write_uint32_be(const uint32_t v) {
+	file.write(std::array<uint8_t, 4> { {
+		static_cast<uint8_t>((v >> 24) & 0xff),
+		static_cast<uint8_t>((v >> 16) & 0xff),
+		static_cast<uint8_t>((v >>  8) & 0xff),
+		static_cast<uint8_t>((v >>  0) & 0xff),
+	} });
+}

firmware/common/png_writer.hpp

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2016 Jared Boone, ShareBrained Technology, Inc.
+ *
+ * This file is part of PortaPack.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __PNG_WRITER_H__
+#define __PNG_WRITER_H__
+
+#include <cstdint>
+#include <cstddef>
+#include <string>
+#include <array>
+
+#include "ui.hpp"
+#include "file.hpp"
+#include "crc.hpp"
+
+class PNGWriter {
+public:
+	explicit PNGWriter(const std::string& filename);
+	~PNGWriter();
+
+	void write_scanline(const std::array<ui::ColorRGB888, 240>& scanline);
+
+private:
+	// TODO: These constants are baked in a few places, do not change blithely.
+	static constexpr int width { 240 };
+	static constexpr int height { 320 };
+
+	File file;
+	int scanline_count { 0 };
+	CRC<32, true, true> crc { 0x04c11db7, 0xffffffff, 0xffffffff };
+	Adler32 adler_32;
+
+	void write_chunk_header(const size_t length, const std::array<uint8_t, 4>& type);
+	void write_chunk_content(const void* const p, const size_t count);
+
+	template<size_t N>
+	void write_chunk_content(const std::array<uint8_t, N>& data) {
+		write_chunk_content(data.data(), sizeof(data));
+	}
+
+	void write_chunk_crc();
+	void write_uint32_be(const uint32_t v);
+};
+
+#endif/*__PNG_WRITER_H__*/