fix g2c_dec_png and make png grid size configurable

CMakeLists.txt

@@ -70,6 +70,9 @@ if(USE_PNG)
   find_package(ZLIB REQUIRED)
   find_package(PkgConfig REQUIRED)
   find_package(PNG REQUIRED)
+  set(PNG_WIDTH_MAX 100000000 CACHE STRING "Default width of PNG grid.")
+  set(PNG_HEIGHT_MAX 100000 CACHE STRING "Default height of PNG grid.")
+  message(STATUS "\tWill build with PNG grid width = ${PNG_WIDTH_MAX} and height = ${PNG_HEIGHT_MAX}")
 else()
   message(STATUS "Will not build PNG support")
 endif()

src/decenc_png.c

@@ -100,7 +100,15 @@ int
 g2c_dec_png(unsigned char *pngbuf, int *width, int *height,
             unsigned char *cout)
 {
-    return dec_png(pngbuf, (g2int *)&width, (g2int *)&height, cout);
+    g2int width8 = *width, height8 = *height;
+    int ret;
+
+    ret = dec_png(pngbuf, &width8, &height8, cout);
+
+    *width = (g2int)width8;
+    *height = (g2int)height8;
+
+    return ret;
 }
 
 /**
@@ -162,6 +170,9 @@ dec_png(unsigned char *pngbuf, g2int *width, g2int *height,
     /* Set new custom read function. */
     png_set_read_fn(png_ptr, (png_voidp)&read_io_ptr, (png_rw_ptr)user_read_data);
 
+    /*     support for larger grids   */
+    png_set_user_limits(png_ptr, G2C_PNG_WIDTH_MAX, G2C_PNG_HEIGHT_MAX);
+
     /* Read and decode PNG stream. */
     png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
 

src/grib2.h.in

@@ -423,6 +423,8 @@ int g2c_param_all(int param_idx, int *g1ver, int *g1val, int *g2disc, int *g2cat
 
 #define G2C_JASPER_MAX_MEM @JASPER_MAX_MEM@ /**< Maximum size for the Jasper memory buffer. */
 
+#define G2C_PNG_WIDTH_MAX @PNG_WIDTH_MAX@ /**< Maximum width of PNG grid */
+#define G2C_PNG_HEIGHT_MAX @PNG_HEIGHT_MAX@ /**< Maximum height of PNG grid */
 /* Error codes for G2 API. */
 #define G2_NO_ERROR 0             /**< Function succeeded. */
 #define G2_CREATE_GRIB_VERSION -1 /**< Wrong GRIB version for g2_create(), must be 2. */

tests/CMakeLists.txt

@@ -72,6 +72,7 @@ set(REF_FILES "gdaswave.t00z.wcoast.0p16.f000.grib2.idx"
   "ref_testgrib2.grb2.degrib2"
   "ref_gdaswave_2.grib1.idx"
   "ref_tst_jasper_warning.txt"
+  "ref_large_png.grib2"
   )
 
 # Copy large files if needed.
@@ -223,6 +224,7 @@ endif()
 if(USE_PNG)
   g2c_test(tst_png)
   g2c_test(tst_addfield2)
+  g2c_test(tst_large_png)
 endif()
 
 # Run these tests only if Jasper or OpenJPEG are linked.

tests/tst_large_png.c

@@ -0,0 +1,48 @@
+/* This is a test for the NCEPLIBS-g2c project. This test is for
+ * the PNG decode function on a large test file.
+ *
+ * Alyson Stahl 11/21/24
+ */
+
+#include "grib2_int.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#define TEST_FILE "data/ref_large_png.grib2"
+
+int
+main()
+{
+    printf("Testing dec_png() on large test file...\n");
+    {
+        float *data;
+        int g2cid, num_data_points;
+        int ret = G2C_NOERROR;
+
+        /* Open the data file. */
+        if ((ret = g2c_open(TEST_FILE, 0, &g2cid)))
+            return ret;
+
+        /* Get the size of the data from message 0, product 0. */
+        if ((ret = g2c_get_prod(g2cid, 0, 0, &num_data_points, NULL)))
+            return ret;
+
+        /* Allocate storage for the data. */
+        if (!(data = malloc(num_data_points * sizeof(float))))
+            return G2C_ERROR;
+
+        /* Get the data from message 0, product 0. */
+        if ((ret = g2c_get_prod(g2cid, 0, 0, NULL, data)))
+            return ret;
+
+        /* Close the data file. */
+        if ((ret = g2c_close(g2cid)))
+            return ret;
+
+        /* Free the memory allocated to hold the data. */
+        free(data);
+    }
+    printf("ok!\n");
+    printf("SUCCESS!\n");
+    return 0;
+}

tests/tst_png.c

@@ -67,6 +67,13 @@ main()
             return G2C_ERROR;
         }
 
+        /* Check that width and height are returned correctly. */
+        if (width_in != 1 || height_in != 1)
+        {
+            printf("png size mismatch: width = %d, height = %d", width_in, height_in);
+            return G2C_ERROR;
+        }
+
         for (i = 0; i < 4; i++)
             if (cout[i] != data[i])
                 return G2C_ERROR;