imageio: add limited PNM support for reading

see: http://netpbm.sourceforge.net/

Only reads P5 and P6 pnm files for now.

Change-Id: I2332a623f803df67455047f570f1cff9f464480a

imageio/pnmdec.c

@@ -0,0 +1,142 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// (limited) PNM decoder
+
+#include "./pnmdec.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "webp/encode.h"
+#include "./imageio_util.h"
+
+// -----------------------------------------------------------------------------
+// PNM decoding
+
+#define MAX_LINE_SIZE 1024
+static const size_t kMinPNMHeaderSize = 3;
+
+static size_t ReadLine(const uint8_t* const data, size_t off, size_t data_size,
+                       char out[MAX_LINE_SIZE + 1], size_t* const out_size) {
+  size_t i = 0;
+  *out_size = 0;
+ redo:
+  for (i = 0; i < MAX_LINE_SIZE && off < data_size; ++i) {
+    out[i] = data[off++];
+    if (out[i] == '\n') break;
+  }
+  if (off < data_size) {
+    if (i == 0) goto redo;         // empty line
+    if (out[0] == '#') goto redo;  // skip comment
+  }
+  out[i] = 0;   // safety sentinel
+  *out_size = i;
+  return off;
+}
+
+static size_t ReadHeader(const uint8_t* const data, size_t data_size,
+                         int* const width, int* const height,
+                         int* const type, int* const max_value) {
+  size_t off = 0;
+  char out[MAX_LINE_SIZE + 1];
+  size_t out_size;
+  if (width == NULL || height == NULL || type == NULL || max_value == NULL) {
+    return 0;
+  }
+  *width = 0;
+  *height = 0;
+  *type = -1;
+  *max_value = 0;
+  if (data == NULL || data_size < kMinPNMHeaderSize) return 0;
+  off = ReadLine(data, off, data_size, out, &out_size);
+  if (off == 0 || sscanf(out, "P%d", type) != 1) return 0;
+  off = ReadLine(data, off, data_size, out, &out_size);
+  if (off == 0 || sscanf(out, "%d %d", width, height) != 2) return 0;
+  off = ReadLine(data, off, data_size, out, &out_size);
+  if (off == 0 || sscanf(out, "%d", max_value) != 1) return 0;
+  return off;
+}
+
+int ReadPNM(const uint8_t* const data, size_t data_size,
+            WebPPicture* const pic, int keep_alpha,
+            struct Metadata* const metadata) {
+  int ok = 0;
+  int width, height, type, max_value;
+  int i, j;
+  uint64_t stride;
+  uint8_t* rgb = NULL, *tmp_rgb;
+  size_t offset;
+
+  offset = ReadHeader(data, data_size, &width, &height,
+                      &type, &max_value);
+  if (offset == 0) goto End;
+  if (type != 5 && type != 6) {
+    fprintf(stderr, "Unsupported P%d PNM format.\n", type);
+    goto End;
+  }
+
+  // Some basic validations.
+  if (pic == NULL) goto End;
+  if (width <= 0 || height <= 0 ||
+      width > WEBP_MAX_DIMENSION || height > WEBP_MAX_DIMENSION) {
+    fprintf(stderr, "Invalid %dx%d dimension for PNM\n", width, height);
+    goto End;
+  }
+
+  stride = 3LL * width;
+  if (stride != (size_t)stride ||
+      !ImgIoUtilCheckSizeArgumentsOverflow(stride, height)) {
+    goto End;
+  }
+  if ((type == 5 && offset + 1LL * width * height > data_size) ||
+      (type == 6 && offset + 3LL * width * height > data_size)) {
+    fprintf(stderr, "Truncated PNM file (P%d).\n", type);
+    goto End;
+  }
+
+  rgb = (uint8_t*)malloc((size_t)stride * height);
+  if (rgb == NULL) goto End;
+
+  // Convert input
+  tmp_rgb = rgb;
+  for (j = 0; j < height; ++j) {
+    if (type == 5) {
+      assert(offset + width <= data_size);
+      for (i = 0; i < width; ++i) {
+        const uint8_t v = data[offset + i];
+        tmp_rgb[3 * i + 0] = tmp_rgb[3 * i + 1] = tmp_rgb[3 * i + 2] = v;
+      }
+      offset += width;
+    } else if (type == 6) {
+      assert(offset + 3LL * width <= data_size);
+      memcpy(tmp_rgb, data + offset, 3 * width * sizeof(*data));
+      offset += 3 * width;
+    }
+    tmp_rgb += stride;
+  }
+
+  // WebP conversion.
+  pic->width = width;
+  pic->height = height;
+  ok = WebPPictureImportRGB(pic, rgb, (int)stride);
+  if (!ok) goto End;
+
+  ok = 1;
+ End:
+  free((void*)rgb);
+
+  (void)metadata;
+  (void)keep_alpha;
+  return ok;
+}
+
+// -----------------------------------------------------------------------------