From f27db5f80b074148aa9b8dd593dc2eefbc9e36ad Mon Sep 17 00:00:00 2001
From: Michael Drake <tlsa@netsurf-browser.org>
Date: Sat, 26 Mar 2022 14:21:18 +0000
Subject: Bitmap: Add format conversion routines.

---
 desktop/bitmap.c | 33 +++++++++++++++++++++++++++++++++
 desktop/bitmap.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+)

(limited to 'desktop')

diff --git a/desktop/bitmap.c b/desktop/bitmap.c
index 48065d080..3e8529a54 100644
--- a/desktop/bitmap.c
+++ b/desktop/bitmap.c
@@ -44,3 +44,36 @@ void bitmap_set_format(const bitmap_fmt_t *bitmap_format)
 	bitmap_fmt.layout = bitmap_sanitise_bitmap_layout(bitmap_fmt.layout);
 	bitmap_layout = bitmap__get_colour_layout(&bitmap_fmt);
 }
+
+/* Exported function, documented in desktop/bitmap.h */
+void bitmap_format_convert(void *bitmap,
+		const bitmap_fmt_t *fmt_from,
+		const bitmap_fmt_t *fmt_to)
+{
+	int width = guit->bitmap->get_width(bitmap);
+	int height = guit->bitmap->get_height(bitmap);
+	uint8_t *buffer = guit->bitmap->get_buffer(bitmap);
+	size_t rowstride = guit->bitmap->get_rowstride(bitmap);
+	struct bitmap_colour_layout to = bitmap__get_colour_layout(fmt_to);
+	struct bitmap_colour_layout from = bitmap__get_colour_layout(fmt_from);
+
+	NSLOG(netsurf, DEEPDEBUG, "Bitmap format conversion (%u --> %u)",
+			fmt_from->layout, fmt_to->layout);
+
+	for (int y = 0; y < height; y++) {
+		uint8_t *row = buffer;
+
+		for (int x = 0; x < width; x++) {
+			const uint32_t px = *((uint32_t *)(void *) row);
+
+			row[to.r] = ((const uint8_t *) &px)[from.r];
+			row[to.g] = ((const uint8_t *) &px)[from.g];
+			row[to.b] = ((const uint8_t *) &px)[from.b];
+			row[to.a] = ((const uint8_t *) &px)[from.a];
+
+			row += sizeof(uint32_t);
+		}
+
+		buffer += rowstride;
+	}
+}
diff --git a/desktop/bitmap.h b/desktop/bitmap.h
index 490928980..af7e9040f 100644
--- a/desktop/bitmap.h
+++ b/desktop/bitmap.h
@@ -121,4 +121,53 @@ static inline enum bitmap_layout bitmap_sanitise_bitmap_layout(
 	return layout;
 }
 
+/**
+ * Convert bitmap from one format to another.
+ *
+ * Note that both formats should be sanitised.
+ *
+ * \param[in]  bitmap  The bitmap to convert.
+ * \param[in]  from    The current bitmap format specifier.
+ * \param[in]  to      The bitmap format to convert to.
+ */
+void bitmap_format_convert(void *bitmap,
+		const bitmap_fmt_t *from,
+		const bitmap_fmt_t *to);
+
+/**
+ * Convert a bitmap to the client bitmap format.
+ *
+ * \param[in]  bitmap       The bitmap to convert.
+ * \param[in]  current_fmt  The current bitmap format specifier.
+ */
+static inline void bitmap_format_to_client(
+		void *bitmap,
+		const bitmap_fmt_t *current_fmt)
+{
+	bitmap_fmt_t from = *current_fmt;
+
+	from.layout = bitmap_sanitise_bitmap_layout(from.layout);
+	if (from.layout != bitmap_fmt.layout) {
+		bitmap_format_convert(bitmap, &from, &bitmap_fmt);
+	}
+}
+
+/**
+ * Convert a bitmap to the client bitmap format.
+ *
+ * \param[in]  bitmap      The bitmap to convert.
+ * \param[in]  target_fmt  The target bitmap format specifier.
+ */
+static inline void bitmap_format_from_client(
+		void *bitmap,
+		const bitmap_fmt_t *target_fmt)
+{
+	bitmap_fmt_t to = *target_fmt;
+
+	to.layout = bitmap_sanitise_bitmap_layout(to.layout);
+	if (to.layout != bitmap_fmt.layout) {
+		bitmap_format_convert(bitmap, &bitmap_fmt, &to);
+	}
+}
+
 #endif
-- 
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