diff options
| -rw-r--r-- | source/fitz/output-png.c | 55 |
1 files changed, 44 insertions, 11 deletions
diff --git a/source/fitz/output-png.c b/source/fitz/output-png.c index f67b1de0..38bfa778 100644 --- a/source/fitz/output-png.c +++ b/source/fitz/output-png.c @@ -214,22 +214,55 @@ png_write_band(fz_context *ctx, fz_band_writer *writer_, int stride, int band_st dp = writer->udata; stride -= w*n; - for (y = 0; y < band_height; y++) + if (writer->super.alpha) { - *dp++ = 1; /* sub prediction filter */ - for (x = 0; x < w; x++) + /* Unpremultiply data */ + for (y = 0; y < band_height; y++) { - for (k = 0; k < n; k++) + *dp++ = 1; /* sub prediction filter */ + for (x = 0; x < w; x++) { - if (x == 0) - dp[k] = sp[k]; - else - dp[k] = sp[k] - sp[k-n]; + int prev[FZ_MAX_COLORS]; + int a = sp[n-1]; + int inva = a ? 256*255/a : 0; + int p; + for (k = 0; k < n-1; k++) + { + int v = (sp[k] * inva + 128)>>8; + p = x ? prev[k] : 0; + prev[k] = v; + v -= p; + dp[k] = v; + } + p = x ? prev[k] : 0; + prev[k] = a; + a -= p; + dp[k] = a; + sp += n; + dp += n; } - sp += n; - dp += n; + sp += stride; + } + } + else + { + for (y = 0; y < band_height; y++) + { + *dp++ = 1; /* sub prediction filter */ + for (x = 0; x < w; x++) + { + for (k = 0; k < n; k++) + { + if (x == 0) + dp[k] = sp[k]; + else + dp[k] = sp[k] - sp[k-n]; + } + sp += n; + dp += n; + } + sp += stride; } - sp += stride; } writer->stream.next_in = (Bytef*)writer->udata; |