add load magick from buffer

try:

irb(main):007:0> png_data = IO.read "k2.png"
irb(main):007:0> require 'vips'
irb(main):007:0> reader = VIPS::MagickReader.new png_data
irb(main):007:0> im = reader.read_buffer
irb(main):007:0> im.x_size
=> 1450

see:

#69

CHANGELOG.md

@@ -1,5 +1,9 @@
 # master 
 
+# Version 0.3.11
+
+* added magick load from buffer [John Cupitt]
+
 # Version 0.3.10
 
 * added webp write [John Cupitt]

Gemfile.lock

@@ -1,7 +1,6 @@
 GEM
   remote: http://rubygems.org/
   specs:
-    rake (10.4.2)
     addressable (2.3.8)
     builder (3.2.2)
     diff-lcs (1.2.5)
@@ -39,6 +38,7 @@ GEM
       multi_xml (~> 0.5)
       rack (~> 1.2)
     rack (1.6.4)
+    rake (10.4.2)
     rdoc (4.2.0)
       json (~> 1.4)
     rdoc-data (4.0.1)

ext/reader.c

@@ -73,6 +73,28 @@ jpeg_buf_internal(VALUE obj, VALUE buf, VALUE shrink, VALUE fail)
     return img_init(cVIPSImage, im_new);
 }
 
+static VALUE
+magick_buf_internal(VALUE obj, VALUE buf)
+{
+    VipsImage *im_new;
+
+    im_new = NULL; 
+
+#if ATLEAST_VIPS( 8, 2 )
+    buf = StringValue(buf);
+
+    if (!(im_new = im_open("", "p")))
+        vips_lib_error();
+
+    if (im_bufmagick2vips(RSTRING_PTR(buf), RSTRING_LEN(buf), im_new, FALSE))
+        vips_lib_error();
+#else
+    rb_raise(eVIPSError, "This method is not implemented in your version of VIPS");
+#endif
+
+    return img_init(cVIPSImage, im_new);
+}
+
 static VALUE
 png_buf_internal(VALUE obj, VALUE buf)
 {
@@ -214,6 +236,10 @@ init_Reader(void)
     rb_define_private_method(magick_reader, "read_internal", magick_read_internal, 2);
     reader_fmt_set(magick_reader, "magick");
 
+    magick_reader = rb_define_class_under(mVIPS, "MagickReader", reader);
+    rb_define_private_method(magick_reader, "buf_internal", magick_buf_internal, 1);
+    reader_fmt_set(magick_reader, "magick");
+
     /*
      * Read Analyze images.
      */

lib/vips/reader.rb

@@ -214,6 +214,12 @@ def read_buffer
     end
   end
 
+  class MagickReader < Reader
+    def read_buffer
+      @_im = buf_internal @path
+    end
+  end
+
   class Image
 
     # Load a ppm file straight to a VIPS Image.

lib/vips/version.rb

@@ -1,3 +1,3 @@
 module VIPS
-  VERSION = "0.3.10"
+  VERSION = "0.3.11"
 end

spec/vips/magick_reader_spec.rb

@@ -14,4 +14,13 @@
     res = VIPS::MagickReader.recognized? @path
     res.should == true
   end
+
+  it "should read a magick file from memory" do
+    if Spec::Helpers.match_vips_version(">= 8.2")
+      png_data = IO.read(@path)
+      reader = VIPS::MagickReader.new(png_data)
+      im = reader.read_buffer
+      im.x_size.should == @image.x_size
+    end
+  end
 end