X-Git-Url: https://git.draconx.ca/gitweb/liblbx.git/blobdiff_plain/e7aea0c6f323c6bbf364093305e60bb78999a23f..4ec9360786d0bb19cffc76818c1a4c33043f68e1:/src/png.c

diff --git a/src/png.c b/src/png.c
index ee5d0a5..288cf77 100644
--- a/src/png.c
+++ b/src/png.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdarg.h>
+#include <stdbool.h>
 #include <setjmp.h>
 
 #include <png.h>
@@ -135,8 +136,47 @@ write_rgba_frame(png_structp png, png_infop info,
 }
 
 static void
-write_index_frame(png_structp png, png_infop info, unsigned char **framedata,
-                                                   struct lbx_colour *palette)
+write_masked_index_frame(png_structp png, png_infop info,
+                         unsigned char **framedata, unsigned char **mask)
+{
+	png_uint_32 width = png_get_image_width(png, info);
+	png_uint_32 height = png_get_image_height(png, info);
+	unsigned char (*row)[2];
+	jmp_buf parent;
+
+	if (width >= PNG_UINT_32_MAX / sizeof *row)
+		fatal(png, -1, "image too wide to allocate row buffer");
+
+	row = png_malloc(png, width * sizeof *row);
+
+	/*
+	 * We need to establish our own error handler to free the row buffer.
+	 * Some care must be taken to save/restore the caller's handler.
+	 */
+	memcpy(&parent, &png_jmpbuf(png), sizeof parent);
+	if (setjmp(png_jmpbuf(png))) {
+		png_free(png, row);
+
+		memcpy(&png_jmpbuf(png), &parent, sizeof parent);
+		png_longjmp(png, 1);
+	}
+
+	png_write_info(png, info);
+	for (png_uint_32 y = 0; y < height; y++) {
+		for (png_uint_32 x = 0; x < width; x++) {
+			row[x][0] = framedata[y][x];
+			row[x][1] = mask[y][x] ? -1 : 0;
+		}
+		png_write_row(png, (void *)row);
+	}
+	png_write_end(png, NULL);
+
+	memcpy(&png_jmpbuf(png), &parent, sizeof parent);
+}
+
+static void
+write_palette_frame(png_structp png, png_infop info,
+                    unsigned char **framedata, struct lbx_colour *palette)
 {
 	png_color png_palette[256];
 
@@ -153,11 +193,19 @@ write_index_frame(png_structp png, png_infop info, unsigned char **framedata,
 	png_write_png(png, info, PNG_TRANSFORM_IDENTITY, NULL);
 }
 
+static void
+write_index_frame(png_structp png, png_infop info, unsigned char **framedata)
+{
+	png_set_rows(png, info, framedata);
+	png_write_png(png, info, PNG_TRANSFORM_IDENTITY, NULL);
+}
+
 int img_output_png(FILE *f, const char *filename,
                    unsigned width, unsigned height,
                    unsigned char **framedata, unsigned char **mask,
 	           struct lbx_colour *palette)
 {
+	bool masked = is_masked(mask, width, height);
 	struct file_info file = { filename, f };
 	png_structp png;
 	png_infop info;
@@ -183,7 +231,7 @@ int img_output_png(FILE *f, const char *filename,
 	png_set_error_fn(png, NULL, error_fn, warning_fn);
 	png_set_write_fn(png, &file, write_data, flush_data);
 
-	if (is_masked(mask, width, height)) {
+	if (palette && masked) {
 		/*
 		 * Indexed colour mode can only be used for images without
 		 * transparency, since indexed PNG requires sacrificing one or
@@ -196,13 +244,27 @@ int img_output_png(FILE *f, const char *filename,
 		             PNG_FILTER_TYPE_DEFAULT);
 
 		write_rgba_frame(png, info, framedata, mask, palette);
-	} else {
+	} else if (palette) {
 		png_set_IHDR(png, info, width, height, 8,
 		             PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
 		             PNG_COMPRESSION_TYPE_DEFAULT,
 		             PNG_FILTER_TYPE_DEFAULT);
 
-		write_index_frame(png, info, framedata, palette);
+		write_palette_frame(png, info, framedata, palette);
+	} else if (masked) {
+		png_set_IHDR(png, info, width, height, 8,
+		             PNG_COLOR_TYPE_GRAY_ALPHA, PNG_INTERLACE_NONE,
+			     PNG_COMPRESSION_TYPE_DEFAULT,
+			     PNG_FILTER_TYPE_DEFAULT);
+
+		write_masked_index_frame(png, info, framedata, mask);
+	} else {
+		png_set_IHDR(png, info, width, height, 8,
+		             PNG_COLOR_TYPE_GRAY, PNG_INTERLACE_NONE,
+			     PNG_COMPRESSION_TYPE_DEFAULT,
+			     PNG_FILTER_TYPE_DEFAULT);
+
+		write_index_frame(png, info, framedata);
 	}
 
 	png_destroy_write_struct(&png, &info);