Add the feature of tile-based decoding to PNG.

There is a relevant patch to the change in zlib:
https://android-git.corp.google.com/g/#change,63173

Change-Id: I617b8740a50af0d75df9f49fa6b88dd2decb36dd

1 files changed, 25 insertions, 0 deletions

diff --git a/pngrio.c b/pngrio.c
index 6978682..4d1220a 100644
--- a/pngrio.c
+++ b/pngrio.c
@@ -38,7 +38,22 @@ png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
       (*(png_ptr->read_data_fn))(png_ptr, data, length);
    else
       png_error(png_ptr, "Call to NULL read function");
+
+#ifdef PNG_INDEX_SUPPORTED
+   png_ptr->total_data_read += length;
+#endif
+}
+
+#ifdef PNG_INDEX_SUPPORTED
+void /* PRIVATE */
+png_seek_data(png_structp png_ptr, png_uint_32 offset)
+{
+   if (png_ptr->seek_data_fn != NULL)
+      (*(png_ptr->seek_data_fn))(png_ptr, offset);
+   else
+      png_error(png_ptr, "Call to NULL seek function");
 }
+#endif
 
 #ifdef PNG_STDIO_SUPPORTED
 /* This is the function that does the actual reading of data.  If you are
@@ -177,4 +192,14 @@ png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
    png_ptr->output_flush_fn = NULL;
 #endif
 }
+
+#ifdef PNG_INDEX_SUPPORTED
+void PNGAPI
+png_set_seek_fn(png_structp png_ptr, png_seek_ptr seek_data_fn)
+{
+   if (png_ptr == NULL)
+      return;
+   png_ptr->seek_data_fn = seek_data_fn;
+}
+#endif
 #endif /* PNG_READ_SUPPORTED */