Add program that demonstrates how to check for the existence of the colorspace extensions

Makefile.am

@@ -73,7 +73,7 @@ libjpeg_la_SOURCES += jsimd_none.c
 endif
 
 bin_PROGRAMS = cjpeg djpeg jpegtran rdjpgcom wrjpgcom tjbench
-noinst_PROGRAMS = tjunittest
+noinst_PROGRAMS = tjunittest jcstest
 
 tjbench_SOURCES = tjbench.c bmp.h bmp.c tjutil.h tjutil.c rdbmp.c rdppm.c \
 	wrbmp.c wrppm.c
@@ -114,6 +114,9 @@ wrjpgcom_SOURCES = wrjpgcom.c
 
 wrjpgcom_LDADD = libjpeg.la
 
+jcstest_SOURCES = jcstest.c
+
+jcstest_LDADD = libjpeg.la
 
 dist_man1_MANS = cjpeg.1 djpeg.1 jpegtran.1 rdjpgcom.1 wrjpgcom.1
 

README-turbo.txt

@@ -227,7 +227,7 @@ colorspace constants:
 Setting cinfo.in_color_space (compression) or cinfo.out_color_space
 (decompression) to one of these values will cause libjpeg-turbo to read the
 red, green, and blue values from (or write them to) the appropriate position in
-the pixel when YUV conversion is performed.
+the pixel when compressing from/decompressing to an RGB buffer.
 
 Your application can check for the existence of these extensions at compile
 time with:
@@ -240,7 +240,7 @@ that doesn't support them will result in a "Bogus input colorspace" error.
 When using the RGBX, BGRX, XBGR, and XRGB colorspaces during decompression, the
 X byte is undefined, and in order to ensure the best performance, libjpeg-turbo
 can set that byte to whatever value it wishes.  If an application expects the X
-byte to be used as an alpha channel, then it should use JCS_EXT_RGBA,
+byte to be used as an alpha channel, then it should specify JCS_EXT_RGBA,
 JCS_EXT_BGRA, JCS_EXT_ABGR, or JCS_EXT_ARGB.  When these colorspace constants
 are used, the X byte is guaranteed to be 0xFF, which is interpreted as opaque.
 
@@ -249,6 +249,9 @@ extensions at compile time with:
 
   #ifdef JCS_ALPHA_EXTENSIONS
 
+jcstest.c, located in the libjpeg-turbo source tree, demonstrates how to check
+for the existence of the colorspace extensions at compile time and run time.
+
 =================================
 libjpeg v7 and v8 API/ABI support
 =================================

jcstest.c

@@ -0,0 +1,126 @@
+/*
+ * Copyright (C)2011 D. R. Commander.  All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * - Neither the name of the libjpeg-turbo Project nor the names of its
+ *   contributors may be used to endorse or promote products derived from this
+ *   software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS",
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* This program demonstrates how to check for the colorspace extension
+   capabilities of libjpeg-turbo at both compile time and run time. */
+
+#include <stdio.h>
+#include <jpeglib.h>
+#include <jerror.h>
+#include <setjmp.h>
+
+#ifndef JCS_EXTENSIONS
+#define JCS_EXT_RGB 6
+#endif
+#if !defined(JCS_EXTENSIONS) || !defined(JCS_ALPHA_EXTENSIONS)
+#define JCS_EXT_RGBA 12
+#endif
+
+static char lasterror[JMSG_LENGTH_MAX] = "No error";
+
+typedef struct _error_mgr {
+  struct jpeg_error_mgr pub;
+  jmp_buf jb;
+} error_mgr;
+
+static void my_error_exit(j_common_ptr cinfo)
+{
+  error_mgr *myerr = (error_mgr *)cinfo->err;
+  (*cinfo->err->output_message)(cinfo);
+  longjmp(myerr->jb, 1);
+}
+
+static void my_output_message(j_common_ptr cinfo)
+{
+  (*cinfo->err->format_message)(cinfo, lasterror);
+}
+
+int main(void)
+{
+  int jcs_valid = -1, jcs_alpha_valid = -1;
+  struct jpeg_compress_struct cinfo;
+  error_mgr jerr;
+
+  printf("libjpeg-turbo colorspace extensions:\n");
+  #if JCS_EXTENSIONS
+  printf("  Present at compile time\n");
+  #else
+  printf("  Not present at compile time\n");
+  #endif
+
+  cinfo.err = jpeg_std_error(&jerr.pub);
+  jerr.pub.error_exit = my_error_exit;
+  jerr.pub.output_message = my_output_message;
+
+  if(setjmp(jerr.jb)) {
+    // this will execute if libjpeg has an error
+    jcs_valid = 0;
+    goto done;
+  }
+
+  jpeg_create_compress(&cinfo);
+  cinfo.input_components = 3;
+  jpeg_set_defaults(&cinfo);
+  cinfo.in_color_space = JCS_EXT_RGB;
+  jpeg_default_colorspace(&cinfo);
+  jcs_valid = 1;
+
+  done:
+  if (jcs_valid)
+    printf("  Working properly\n");
+  else
+    printf("  Not working properly.  Error returned was:\n    %s\n",
+           lasterror);
+
+  printf("libjpeg-turbo alpha colorspace extensions:\n");
+  #if JCS_ALPHA_EXTENSIONS
+  printf("  Present at compile time\n");
+  #else
+  printf("  Not present at compile time\n");
+  #endif
+
+  if(setjmp(jerr.jb)) {
+    // this will execute if libjpeg has an error
+    jcs_alpha_valid = 0;
+    goto done2;
+  }
+
+  cinfo.in_color_space = JCS_EXT_RGBA;
+  jpeg_default_colorspace(&cinfo);
+  jcs_alpha_valid = 1;
+
+  done2:
+  if (jcs_alpha_valid)
+    printf("  Working properly\n");
+  else
+    printf("  Not working properly.  Error returned was:\n    %s\n",
+           lasterror);
+
+  jpeg_destroy_compress(&cinfo);
+  return 0;
+}

sharedlib/CMakeLists.txt

@@ -53,6 +53,9 @@ add_executable(jpegtran ../jpegtran.c ../cdjpeg.c ../rdswitch.c ../transupp.c)
 target_link_libraries(jpegtran jpeg)
 set_property(TARGET jpegtran PROPERTY COMPILE_FLAGS "-DUSE_SETMODE")
 
+add_executable(jcstest ../jcstest.c)
+target_link_libraries(jcstest jpeg)
+
 install(TARGETS jpeg cjpeg djpeg jpegtran
   ARCHIVE DESTINATION lib
   LIBRARY DESTINATION lib