From 4b52630c1ee0db380263a49d0e90e761c6834481 Mon Sep 17 00:00:00 2001
From: Abdelrahman <said.abdelrahman89@gmail.com>
Date: Thu, 2 May 2024 22:00:32 +0100
Subject: [PATCH] Implement reading RGB and RGBA images

---
 src/tiff/tiffread.c | 58 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 51 insertions(+), 7 deletions(-)

diff --git a/src/tiff/tiffread.c b/src/tiff/tiffread.c
index bb8a301..cd6a46d 100644
--- a/src/tiff/tiffread.c
+++ b/src/tiff/tiffread.c
@@ -3,6 +3,7 @@
 #include "endianness.h"
 #include "image.h"
 #include "mem_arena.h"
+#include <assert.h>
 #include <math.h>
 #include <netinet/in.h>
 #include <stdbool.h>
@@ -35,7 +36,8 @@
 TiffHdr read_tiff_header(FILE *fp);
 TiffIFD read_ifd(FILE *fp, const TiffHdr *header, u32 offset, Arena *arena);
 TiffImage read_fields(FILE *fp, const TiffHdr *header, const TiffIFD *ifd);
-bool read_strip_data(FILE *fp, const TiffImage *img, TiffStrip *strips);
+bool read_strip_data(FILE *fp, const TiffHdr *header, const TiffImage *img,
+                     TiffStrip *strips);
 void read_strips(FILE *fp, const TiffImage *img, const TiffStrip *strips,
                  Pixel *buf);
 bool read_field(const TiffField *field, TiffImage *img,
@@ -96,7 +98,7 @@ Image *read_baseline_tiff(const char *file, Arena *arena) {
     goto READ_BASELINE_DESTROY_ARENA;
   }
 
-  if (!read_strip_data(fp, &img, strips)) {
+  if (!read_strip_data(fp, &header, &img, strips)) {
     goto READ_BASELINE_DESTROY_ARENA;
   }
 
@@ -260,7 +262,8 @@ READ_FIELDS_RETURN_IMAGE:
   return img_out;
 }
 
-bool read_strip_data(FILE *fp, const TiffImage *img, TiffStrip *strips) {
+bool read_strip_data(FILE *fp, const TiffHdr *header, const TiffImage *img,
+                     TiffStrip *strips) {
   if (!fp || !img || !strips) {
     return false;
   }
@@ -285,6 +288,21 @@ bool read_strip_data(FILE *fp, const TiffImage *img, TiffStrip *strips) {
     if (offsets_total_bytes > sizeof(u32)) {
       u32 offset = img->strip_offsets.long_val + offset_size * i;
       read_from_file_with_offset(fp, &(strip->offset), offset_size, offset);
+
+      switch (header->order) {
+      case TIFF_ORDER_BIG_ENDIAN:
+        if (IS_LITTLE_ENDIAN) {
+          strip->offset = offset_size > sizeof(u16) ? ntohl(strip->offset)
+                                                    : ntohs(strip->offset);
+        }
+        break;
+      case TIFF_ORDER_LITTLE_ENDIAN:
+        if (IS_BIG_ENDIAN) {
+          strip->offset = offset_size > sizeof(u16) ? htonl(strip->offset)
+                                                    : htons(strip->offset);
+        }
+        break;
+      }
     } else {
       memcpy(&(strip->offset), &(img->strip_offsets.long_val), offset_size);
     }
@@ -292,6 +310,23 @@ bool read_strip_data(FILE *fp, const TiffImage *img, TiffStrip *strips) {
     if (byte_count_total_bytes > sizeof(u32)) {
       u32 offset = img->strip_byte_counts.long_val + counts_size * i;
       read_from_file_with_offset(fp, &(strip->byte_count), counts_size, offset);
+
+      switch (header->order) {
+      case TIFF_ORDER_BIG_ENDIAN:
+        if (IS_LITTLE_ENDIAN) {
+          strip->byte_count = counts_size > sizeof(u16)
+                                  ? ntohl(strip->byte_count)
+                                  : ntohs(strip->byte_count);
+        }
+        break;
+      case TIFF_ORDER_LITTLE_ENDIAN:
+        if (IS_BIG_ENDIAN) {
+          strip->byte_count = counts_size > sizeof(u16)
+                                  ? htonl(strip->byte_count)
+                                  : htons(strip->byte_count);
+        }
+        break;
+      }
     } else {
       memcpy(&(strip->byte_count), &(img->strip_byte_counts.long_val),
              counts_size);
@@ -303,15 +338,24 @@ bool read_strip_data(FILE *fp, const TiffImage *img, TiffStrip *strips) {
 
 void read_strips(FILE *fp, const TiffImage *img, const TiffStrip *strips,
                  Pixel *buf) {
+  assert((img->sample_count == 3 || img->sample_count == 4) &&
+         "Only RGB or RGBA images supported");
+
+  u64 position = 0;
   for (u64 i = 0; i < img->strip_count; ++i) {
     const TiffStrip *strip = &(strips[i]);
 
-    for (u64 j = 0; j < img->image_width * img->image_length; ++j) {
-      Pixel *p = &(buf[j]);
+    for (u64 j = 0; j < strip->byte_count / img->sample_count; ++j) {
+      Pixel *p = &(buf[position]);
 
-      read_from_file_with_offset(fp, p, 3, strip->offset + j * 3);
+      read_from_file_with_offset(fp, p, img->sample_count,
+                                 strip->offset + j * img->sample_count);
 
-      p->a = 255;
+      if (img->sample_count == 3) {
+        p->a = 255;
+      }
+
+      ++position;
     }
   }
 }