added examples/decode_minimal.c

As a complement to encode_minimal.c, this example presents usage of the
decoder with less code than already is in other examples.

Author: MartinPulec

examples/CMakeLists.txt

@@ -12,6 +12,9 @@ target_link_libraries(encode_minimal gpujpeg)
 add_executable(encode_raw encode_raw.c)
 target_link_libraries(encode_raw gpujpeg)
 
+add_executable(decode_minimal decode_minimal.c)
+target_link_libraries(decode_minimal gpujpeg)
+
 add_executable(decode_to_pnm decode_to_pnm.c)
 target_link_libraries(decode_to_pnm gpujpeg)
 

examples/decode_minimal.c

@@ -0,0 +1,47 @@
+#include <assert.h>
+#include <libgpujpeg/gpujpeg_decoder.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static uint8_t*
+load_file(const char* fname, size_t* jpeg_len)
+{
+    FILE* in_file = fopen(fname, "rb");
+    assert(in_file != NULL);
+    fseek(in_file, 0, SEEK_END);
+    *jpeg_len = ftell(in_file);
+    uint8_t* image_data = malloc(*jpeg_len);
+    fseek(in_file, 0, SEEK_SET);
+    fread(image_data, *jpeg_len, 1, in_file);
+    fclose(in_file);
+    return image_data;
+}
+
+int
+main(int argc, char* argv[])
+{
+    if ( argc <= 1 ) {
+        printf("usage:\n%s <jpg>\n", argv[0]);
+        return 1;
+    }
+    int ret = EXIT_SUCCESS;
+    size_t jpeg_len = 0;
+    uint8_t* jpeg_data = load_file(argv[1], &jpeg_len);
+    struct gpujpeg_decoder* decoder = gpujpeg_decoder_create(0);
+    assert(decoder != NULL);
+    struct gpujpeg_decoder_output dec_output;
+    gpujpeg_decoder_output_set_default(&dec_output);
+    char fname[] = "out.XXX";
+    if ( gpujpeg_decoder_decode(decoder, jpeg_data, jpeg_len, &dec_output) != 0 ||
+         gpujpeg_image_save_to_file(fname, dec_output.data, dec_output.data_size, &dec_output.param_image) != 0 ) {
+        fprintf(stderr, "decode or write failed!\n");
+        ret = EXIT_FAILURE;
+    }
+    else {
+        printf("Output written to %s\n", fname);
+    }
+    free(jpeg_data);
+    gpujpeg_decoder_destroy(decoder);
+    return ret;
+}