[PATCH v4 1/1] apps: cam: Add support for PPM output format

[Milan Zamazal]

When file output is requested from cam app, it simply dumps the processed data
and it must be converted to a readable image format manually.  Let's add support
for PPM output file format to make files produced by cam directly readable by
image display and processing software.

For now, only BGR888 output format, which is the simplest one to use, is
supported but nothing prevents adding support for other output formats if
needed.  Nevertheless, they would typically need byte reordering or other
conversions for PPM file format.  It may be better to find a way to dump the
image data in other output formats directly using some of the already existing
file formats or raw file format converters.

Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/apps/cam/file_sink.cpp     | 11 +++++++
 src/apps/cam/main.cpp          |  2 ++
 src/apps/common/meson.build    |  1 +
 src/apps/common/ppm_writer.cpp | 53 ++++++++++++++++++++++++++++++++++
 src/apps/common/ppm_writer.h   | 20 +++++++++++++
 5 files changed, 87 insertions(+)
 create mode 100644 src/apps/common/ppm_writer.cpp
 create mode 100644 src/apps/common/ppm_writer.h

diff --git a/src/apps/cam/file_sink.cpp b/src/apps/cam/file_sink.cpp
index dca350c4..906b50e6 100644
--- a/src/apps/cam/file_sink.cpp
+++ b/src/apps/cam/file_sink.cpp
@@ -17,6 +17,7 @@
 
 #include "../common/dng_writer.h"
 #include "../common/image.h"
+#include "../common/ppm_writer.h"
 
 #include "file_sink.h"
 
@@ -76,6 +77,7 @@ void FileSink::writeBuffer(const Stream *stream, FrameBuffer *buffer,
 #ifdef HAVE_TIFF
 	bool dng = filename.find(".dng", filename.size() - 4) != std::string::npos;
 #endif /* HAVE_TIFF */
+	bool ppm = filename.find(".ppm", filename.size() - 4) != std::string::npos;
 
 	if (filename.empty() || filename.back() == '/')
 		filename += "frame-#.bin";
@@ -102,6 +104,15 @@ void FileSink::writeBuffer(const Stream *stream, FrameBuffer *buffer,
 		return;
 	}
 #endif /* HAVE_TIFF */
+	if (ppm) {
+		ret = PPMWriter::write(filename.c_str(), stream->configuration(),
+				       image->data(0));
+		if (ret < 0)
+			std::cerr << "failed to write PPM file `" << filename
+				  << "'" << std::endl;
+
+		return;
+	}
 
 	fd = open(filename.c_str(), O_CREAT | O_WRONLY |
 		  (pos == std::string::npos ? O_APPEND : O_TRUNC),
diff --git a/src/apps/cam/main.cpp b/src/apps/cam/main.cpp
index 179cc376..1aabee01 100644
--- a/src/apps/cam/main.cpp
+++ b/src/apps/cam/main.cpp
@@ -154,6 +154,8 @@ int CamApp::parseOptions(int argc, char *argv[])
 			 "If the file name ends with '.dng', then the frame will be written to\n"
 			 "the output file(s) in DNG format.\n"
 #endif
+			 "If the file name ends with '.ppm', then the frame will be written to\n"
+			 "the output file(s) in PPM format.\n"
 			 "The default file name is 'frame-#.bin'.",
 			 "file", ArgumentOptional, "filename", false,
 			 OptCamera);
diff --git a/src/apps/common/meson.build b/src/apps/common/meson.build
index 479326cd..5b683390 100644
--- a/src/apps/common/meson.build
+++ b/src/apps/common/meson.build
@@ -3,6 +3,7 @@
 apps_sources = files([
     'image.cpp',
     'options.cpp',
+    'ppm_writer.cpp',
     'stream_options.cpp',
 ])
 
diff --git a/src/apps/common/ppm_writer.cpp b/src/apps/common/ppm_writer.cpp
new file mode 100644
index 00000000..04a49499
--- /dev/null
+++ b/src/apps/common/ppm_writer.cpp
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024 Red Hat, Inc.
+ *
+ * ppm_writer.cpp - PPM writer
+ */
+
+#include <fstream>
+#include <iostream>
+
+#include <libcamera/formats.h>
+#include <libcamera/pixel_format.h>
+
+#include "ppm_writer.h"
+
+using namespace libcamera;
+
+int PPMWriter::write(const char *filename,
+		     const StreamConfiguration &config,
+		     const Span<uint8_t> &data)
+{
+	if (config.pixelFormat != formats::BGR888) {
+		std::cerr << "Only BGR888 output pixel format is supported ("
+			  << config.pixelFormat << " requested)" << std::endl;
+		return -EINVAL;
+	}
+
+	std::ofstream output(filename, std::ios::binary);
+	if (!output) {
+		std::cerr << "Failed to open ppm file: " << filename << std::endl;
+		return -EINVAL;
+	}
+
+	output << "P6" << std::endl
+	       << config.size.width << " " << config.size.height << std::endl
+	       << "255" << std::endl;
+	if (!output) {
+		std::cerr << "Failed to write the file header" << std::endl;
+		return -EINVAL;
+	}
+
+	const unsigned int rowLength = config.size.width * 3;
+	const char *row = reinterpret_cast<const char *>(data.data());
+	for (unsigned int y = 0; y < config.size.height; y++, row += config.stride) {
+		output.write(row, rowLength);
+		if (!output) {
+			std::cerr << "Failed to write image data at row " << y << std::endl;
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
diff --git a/src/apps/common/ppm_writer.h b/src/apps/common/ppm_writer.h
new file mode 100644
index 00000000..4c38f5ce
--- /dev/null
+++ b/src/apps/common/ppm_writer.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Red Hat, Inc.
+ *
+ * ppm_writer.h - PPM writer
+ */
+
+#pragma once
+
+#include <libcamera/base/span.h>
+
+#include <libcamera/stream.h>
+
+class PPMWriter
+{
+public:
+	static int write(const char *filename,
+			 const libcamera::StreamConfiguration &config,
+			 const libcamera::Span<uint8_t> &data);
+};
-- 
2.42.0