From 3a1ebbcf6d5b34dcc0eebf6de4859b50d7d99ed3 Mon Sep 17 00:00:00 2001 From: "Adam D. Ruppe" Date: Mon, 6 Jun 2016 10:55:51 -0400 Subject: [PATCH] ketmar insertChunk --- png.d | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/png.d b/png.d index 8b3bd7a..4e7721f 100644 --- a/png.d +++ b/png.d @@ -367,6 +367,35 @@ struct PNG { } return null; } + + // Insert chunk before IDAT. PNG specs allows to drop all chunks after IDAT, + // so we have to insert our custom chunks right before it. + // Use `Chunk.create()` to create new chunk, and then `insertChunk()` to add it. + // Return `true` if we did replacement. + bool insertChunk (Chunk* chk, bool replaceExisting=false) { + if (chk is null) return false; // just in case + // use reversed loop, as "IDAT" is usually present, and it is usually the last, + // so we will somewhat amortize painter's algorithm here. + foreach_reverse (immutable idx, ref cc; chunks) { + if (replaceExisting && cc.type == chk.type) { + // replace existing chunk, the easiest case + chunks[idx] = *chk; + return true; + } + if (cast(string)cc.type == "IDAT") { + // ok, insert it; and don't use phobos + chunks.length += 1; + foreach_reverse (immutable c; idx+1..chunks.length) chunks.ptr[c] = chunks.ptr[c-1]; + chunks.ptr[idx] = *chk; + return false; + } + } + chunks ~= *chk; + return false; + } + + // Convenient wrapper for `insertChunk()`. + bool replaceChunk (Chunk* chk) { return insertChunk(chk, true); } } // this is just like writePng(filename, pngFromImage(image)), but it manages