read 12 bit PNGs (patch from Tobias Wood)

svn path=/branches/v0_98_5_maint/; revision=7028

Author: astraw

src/_png.cpp

@@ -208,38 +208,37 @@ _png_module::read_png(const Py::Tuple& args) {
 
   png_init_io(png_ptr, fp);
   png_set_sig_bytes(png_ptr, 8);
-
   png_read_info(png_ptr, info_ptr);
 
   png_uint_32 width = info_ptr->width;
   png_uint_32 height = info_ptr->height;
-  bool do_gray_conversion = (info_ptr->bit_depth < 8 &&
-                             info_ptr->color_type == PNG_COLOR_TYPE_GRAY);
 
   int bit_depth = info_ptr->bit_depth;
-  if (bit_depth == 16) {
-    png_set_strip_16(png_ptr);
-  } else if (bit_depth < 8) {
+  
+  // Unpack 1, 2, and 4-bit images
+  if (bit_depth < 8)
     png_set_packing(png_ptr);
-  }
 
-  // convert misc color types to rgb for simplicity
-  if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY ||
-      info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
-    png_set_gray_to_rgb(png_ptr);
-  } else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) {
+  // If sig bits are set, shift data
+  png_color_8p sig_bit;
+  if ((info_ptr->color_type != PNG_COLOR_TYPE_PALETTE) && png_get_sBIT(png_ptr, info_ptr, &sig_bit))
+    png_set_shift(png_ptr, sig_bit);
+
+  // Convert big endian to little
+  if (bit_depth == 16)
+    png_set_swap(png_ptr);
+
+  // Convert palletes to full RGB
+  if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
     png_set_palette_to_rgb(png_ptr);
-  }
+  
+  // If there's an alpha channel convert gray to RGB
+  if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+    png_set_gray_to_rgb(png_ptr);
 
   png_set_interlace_handling(png_ptr);
   png_read_update_info(png_ptr, info_ptr);
 
-  bool rgba = info_ptr->color_type == PNG_COLOR_TYPE_RGBA;
-  if ( (info_ptr->color_type != PNG_COLOR_TYPE_RGB) && !rgba) {
-    std::cerr << "Found color type " << (int)info_ptr->color_type  << std::endl;
-    throw Py::RuntimeError("_image_module::readpng: cannot handle color_type");
-  }
-
   /* read file */
   if (setjmp(png_jmpbuf(png_ptr)))
     throw Py::RuntimeError("_image_module::readpng: error during read_image");
@@ -255,37 +254,36 @@ _png_module::read_png(const Py::Tuple& args) {
   npy_intp dimensions[3];
   dimensions[0] = height;  //numrows
   dimensions[1] = width;   //numcols
-  dimensions[2] = 4;
-
-  PyArrayObject *A = (PyArrayObject *) PyArray_SimpleNew(3, dimensions, PyArray_FLOAT);
-
-  if (do_gray_conversion) {
-    float max_value = (float)((1L << bit_depth) - 1);
-    for (png_uint_32 y = 0; y < height; y++) {
-      png_byte* row = row_pointers[y];
-      for (png_uint_32 x = 0; x < width; x++) {
-        float value = row[x] / max_value;
-        size_t offset = y*A->strides[0] + x*A->strides[1];
-        *(float*)(A->data + offset + 0*A->strides[2]) = value;
-        *(float*)(A->data + offset + 1*A->strides[2]) = value;
-        *(float*)(A->data + offset + 2*A->strides[2]) = value;
-        *(float*)(A->data + offset + 3*A->strides[2]) = 1.0f;
-      }
-    }
-  } else {
-    for (png_uint_32 y = 0; y < height; y++) {
-      png_byte* row = row_pointers[y];
-      for (png_uint_32 x = 0; x < width; x++) {
-        png_byte* ptr = (rgba) ? &(row[x*4]) : &(row[x*3]);
-        size_t offset = y*A->strides[0] + x*A->strides[1];
-        *(float*)(A->data + offset + 0*A->strides[2]) = (float)(ptr[0]/255.0);
-        *(float*)(A->data + offset + 1*A->strides[2]) = (float)(ptr[1]/255.0);
-        *(float*)(A->data + offset + 2*A->strides[2]) = (float)(ptr[2]/255.0);
-        *(float*)(A->data + offset + 3*A->strides[2]) = rgba ? (float)(ptr[3]/255.0) : 1.0f;
-      }
+  if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
+    dimensions[2] = 4;     //RGBA images
+  else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
+    dimensions[2] = 3;     //RGB images
+  else
+    dimensions[2] = 1;     //Greyscale images
+  //For gray, return an x by y array, not an x by y by 1
+  int num_dims  = (info_ptr->color_type & PNG_COLOR_MASK_COLOR) ? 3 : 2;
+  
+  double max_value = (1 << ((bit_depth < 8) ? 8 : bit_depth)) - 1;
+  PyArrayObject *A = (PyArrayObject *) PyArray_SimpleNew(num_dims, dimensions, PyArray_FLOAT);
+
+  for (png_uint_32 y = 0; y < height; y++) {
+    png_byte* row = row_pointers[y];
+	for (png_uint_32 x = 0; x < width; x++) {
+	  size_t offset = y*A->strides[0] + x*A->strides[1];
+	  if (bit_depth == 16) {
+	    png_uint_16* ptr = &reinterpret_cast<png_uint_16*> (row)[x * dimensions[2]];
+		for (png_uint_32 p = 0; p < dimensions[2]; p++)
+	      *(float*)(A->data + offset + p*A->strides[2]) = (float)(ptr[p]) / max_value;
+	  } else {
+	    png_byte* ptr = &(row[x * dimensions[2]]);
+	    for (png_uint_32 p = 0; p < dimensions[2]; p++)
+		{
+	      *(float*)(A->data + offset + p*A->strides[2]) = (float)(ptr[p]) / max_value;
+	    }
+	  }
     }
   }
-
+  
   //free the png memory
   png_read_end(png_ptr, info_ptr);
   png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);