Add image overlay support to possession mode lenses

config/mods/lens_overlay_test/creatrs/imp.cfg

@@ -0,0 +1,4 @@
+; IMP with helmet visor overlay lens + mist effect
+
+[senses]
+EyeEffect = TEST_WITH_MIST

config/mods/lens_overlay_test/fxdata/lenses.cfg

@@ -0,0 +1,15 @@
+; Test Lens Overlay Configuration for KeeperFX
+; This demonstrates the new ZIP+JSON lens overlay system
+
+; NEW TEST LENS WITH OVERLAY GRAPHIC ONLY
+[lens15]
+Name = LENS_HELMET_VISOR
+; This uses the new overlay system - name references the overlay in lenses.json
+OVERLAY = TUNNELER_VISOR 200
+; Alpha transparency: 0-255 (0=fully transparent, 255=fully opaque)
+
+[lens16]
+Name = TEST_WITH_MIST
+; You can combine overlays with mist effects
+Mist = frac09.raw 4 0
+OVERLAY = TUNNELER_VISOR 180

src/config_lenses.c

@@ -26,6 +26,7 @@
 
 #include "config.h"
 #include "thing_doors.h"
+#include "custom_sprites.h"
 
 #include "keeperfx.hpp"
 #include "post_inc.h"
@@ -49,6 +50,7 @@ const struct ConfigFileData keeper_lenses_file_data = {
 static int64_t value_mist(const struct NamedField* named_field, const char* value_text, const struct NamedFieldSet* named_fields_set, int idx, const char* src_str, unsigned char flags);
 static int64_t value_pallete(const struct NamedField* named_field, const char* value_text, const struct NamedFieldSet* named_fields_set, int idx, const char* src_str, unsigned char flags);
 static int64_t value_displace(const struct NamedField* named_field, const char* value_text, const struct NamedFieldSet* named_fields_set, int idx, const char* src_str, unsigned char flags);
+static int64_t value_overlay(const struct NamedField* named_field, const char* value_text, const struct NamedFieldSet* named_fields_set, int idx, const char* src_str, unsigned char flags);
 
 const struct NamedField lenses_data_named_fields[] = {
     //name           //pos    //field                                           //default //min     //max    //NamedCommand
@@ -60,6 +62,8 @@ const struct NamedField lenses_data_named_fields[] = {
     {"DISPLACEMENT",      1, field(lenses_conf.lenses[0].displace_magnitude),       0,        0,      511, NULL,         value_default,   assign_default},
     {"DISPLACEMENT",      2, field(lenses_conf.lenses[0].displace_period),          1,        0,      511, NULL,         value_displace,  assign_default},
     {"PALETTE",           0, field(lenses_conf.lenses[0].palette),                  0,        0,        0, NULL,         value_pallete,   assign_null},
+    {"OVERLAY",           0, field(lenses_conf.lenses[0].overlay_file),             0,        0,        0, NULL,         value_overlay,   assign_null},
+    {"OVERLAY",           1, field(lenses_conf.lenses[0].overlay_alpha),          128,        0,      255, NULL,         value_default,   assign_default},
     {NULL},
 };
 
@@ -107,6 +111,39 @@ static int64_t value_pallete(const struct NamedField* named_field, const char* v
     return 0;
 }
 
+static int64_t value_overlay(const struct NamedField* named_field, const char* value_text, const struct NamedFieldSet* named_fields_set, int idx, const char* src_str, unsigned char flags)
+{
+    SYNCLOG("value_overlay called: argnum=%d, value='%s', lens=%d", named_field->argnum, value_text, idx);
+
+    if (value_text == NULL || value_text[0] == '\0') {
+        CONFWRNLOG("Empty overlay name for \"%s\" parameter in [%s%d] block of lens.cfg file.",
+            named_field->name, named_fields_set->block_basename, idx);
+        return 0;
+    }
+
+    lenses_conf.lenses[idx].flags |= LCF_HasOverlay;
+    struct LensConfig* lenscfg = &lenses_conf.lenses[idx];
+
+    // Only store the overlay name when processing position 0 (the name field), pos 1 is for alpha value
+    if (named_field->argnum == 0)
+    {
+        strncpy(lenscfg->overlay_file, value_text, DISKPATH_SIZE - 1);
+        lenscfg->overlay_file[DISKPATH_SIZE - 1] = '\0';
+
+        lenscfg->overlay_data = NULL;
+        lenscfg->overlay_width = 0;
+        lenscfg->overlay_height = 0;
+
+        SYNCDBG(9, "Registered overlay name '%s' for lens %d", value_text, idx);
+    }
+    else
+    {
+        SYNCLOG("Skipping overlay name storage for argnum=%d (alpha value)", named_field->argnum);
+    }
+
+    return 0;
+}
+
 static TbBool load_lenses_config_file(const char *fname, unsigned short flags)
 {
     SYNCDBG(0,"%s file \"%s\".",((flags & CnfLd_ListOnly) == 0)?"Reading":"Parsing",fname);

src/config_lenses.h

@@ -35,6 +35,7 @@ enum LensConfigFlags {
     LCF_HasMist     = 0x01,
     LCF_HasDisplace = 0x02,
     LCF_HasPalette  = 0x04,
+    LCF_HasOverlay  = 0x08,
 };
 
 struct LensConfig {
@@ -47,6 +48,12 @@ struct LensConfig {
     short displace_kind;
     short displace_magnitude;
     short displace_period;
+    char overlay_file[DISKPATH_SIZE];
+    char overlay_mod_dir[DISKPATH_SIZE];  // Mod directory for overlay, empty for base game
+    unsigned char *overlay_data;
+    int overlay_width;
+    int overlay_height;
+    short overlay_alpha;
 };
 
 struct LensesConfig {