tweak baldurk's hdr implementation

stb_image_write.h

@@ -1,16 +1,16 @@
-/* stb_image_write - v0.95 - public domain - http://nothings.org/stb/stb_image_write.h
+/* stb_image_write - v0.96 - public domain - http://nothings.org/stb/stb_image_write.h
    writes out PNG/BMP/TGA images to C stdio - Sean Barrett 2010
                             no warranty implied; use at your own risk
 
 
-Before including,
+   Before #including,
 
-    #define STB_IMAGE_WRITE_IMPLEMENTATION
+       #define STB_IMAGE_WRITE_IMPLEMENTATION
 
-in the file that you want to have the implementation.
+   in the file that you want to have the implementation.
 
-Will probably not work correctly with strict-aliasing optimizations.
 
+   Will probably not work correctly with strict-aliasing optimizations.
 
 ABOUT:
 
@@ -56,6 +56,17 @@ USAGE:
    HDR expects linear float data. Since the format is always 32-bit rgb(e)
    data, alpha (if provided) is discarded, and for monochrome data it is
    replicated across all three channels.
+
+CREDITS:
+
+   PNG/BMP/TGA
+      Sean Barrett
+   HDR
+      Baldur Karlsson
+   TGA monochrome:
+      Jean-Sebastien Guay
+   Bugfixes:
+      Chribba@github
 */
 
 #ifndef INCLUDE_STB_IMAGE_WRITE_H
@@ -65,10 +76,10 @@ USAGE:
 extern "C" {
 #endif
 
-extern int stbi_write_png(char const *filename, int w, int h, int comp, const void *data, int stride_in_bytes);
-extern int stbi_write_bmp(char const *filename, int w, int h, int comp, const void *data);
-extern int stbi_write_tga(char const *filename, int w, int h, int comp, const void *data);
-extern int stbi_write_hdr(char const *filename, int w, int h, int comp, const void *data);
+extern int stbi_write_png(char const *filename, int w, int h, int comp, const void  *data, int stride_in_bytes);
+extern int stbi_write_bmp(char const *filename, int w, int h, int comp, const void  *data);
+extern int stbi_write_tga(char const *filename, int w, int h, int comp, const void  *data);
+extern int stbi_write_hdr(char const *filename, int w, int h, int comp, const float *data);
 
 #ifdef __cplusplus
 }
@@ -83,6 +94,7 @@ extern int stbi_write_hdr(char const *filename, int w, int h, int comp, const vo
 #include <stdio.h>
 #include <string.h>
 #include <assert.h>
+#include <math.h>
 
 typedef unsigned int stbiw_uint32;
 typedef int stb_image_write_test[sizeof(stbiw_uint32)==4 ? 1 : -1];
@@ -193,7 +205,7 @@ int stbi_write_tga(char const *filename, int x, int y, int comp, const void *dat
 
 // *************************************************************************************************
 // Radiance RGBE HDR writer
-// originally by Baldur Karlsson
+// by Baldur Karlsson
 #define stbiw__max(a, b)  ((a) > (b) ? (a) : (b))
 
 void stbiw__linear_to_rgbe(unsigned char *rgbe, float *linear)
@@ -204,7 +216,7 @@ void stbiw__linear_to_rgbe(unsigned char *rgbe, float *linear)
    if (maxcomp < 1e-32) {
       rgbe[0] = rgbe[1] = rgbe[2] = rgbe[3] = 0;
    } else {
-      maxcomp = (float) frexp(maxcomp, &exponent) * 256.0f/maxcomp;
+      float normalize = (float) frexp(maxcomp, &exponent) * 256.0f/maxcomp;
 
       rgbe[0] = (unsigned char)(linear[0] * maxcomp);
       rgbe[1] = (unsigned char)(linear[1] * maxcomp);
@@ -216,6 +228,7 @@ void stbiw__linear_to_rgbe(unsigned char *rgbe, float *linear)
 void stbiw__write_rle_data(FILE *f, int length, unsigned char databyte)
 {
    unsigned char lengthbyte = 0x80 | (unsigned char)(length & 0x7f);
+   assert(length <= 0x7f);
    fwrite(&lengthbyte, 1, 1, f);
    fwrite(&databyte, 1, 1, f);
 }
@@ -223,11 +236,12 @@ void stbiw__write_rle_data(FILE *f, int length, unsigned char databyte)
 void stbiw__write_nonrle_data(FILE *f, int length, unsigned char *data)
 {
    unsigned char lengthbyte = (unsigned char )(length & 0xff);
+   assert(length <= 0x7f);
    fwrite(&lengthbyte, 1, 1, f);
    fwrite(data, length, 1, f);
 }
 
-void stbiw__write_hdr_scanline(FILE *f, int width, int comp, unsigned char *scratch, float *scanline)
+void stbiw__write_hdr_scanline(FILE *f, int width, int comp, unsigned char *scratch, const float *scanline)
 {
    unsigned char scanlineheader[4] = { 2, 2, 0, 0 };
    unsigned char rgbe[4];
@@ -324,26 +338,28 @@ void stbiw__write_hdr_scanline(FILE *f, int width, int comp, unsigned char *scra
    }
 }
 
-int stbi_write_hdr(char const *filename, int x, int y, int comp, const void *data)
+int stbi_write_hdr(char const *filename, int x, int y, int comp, const float *data)
 {
    int i;
    FILE *f;
-   unsigned char *scratch;
-   if (y <= 0 || x <= 0) return 0;
+   if (y <= 0 || x <= 0 || data == NULL) return 0;
    f = fopen(filename, "wb");
    if (f) {
-      float *scanline = (float *)data;
       /* Each component is stored separately. Allocate scratch space for full output scanline. */
-      scratch = (unsigned char *) malloc(x*4); if (!scanline) { fclose(f); return 0; }
-      fprintf(f, "#?RADIANCE\n# Written by stb_image_write.h\nFORMAT=32-bit_rle_rgbe\n");
-      fprintf(f, "EXPOSURE=          1.0000000000000\n\n-Y %d +X %d\n", y, x);
-      for(i=0; i < y; i++) stbiw__write_hdr_scanline(f, x, comp, scratch, scanline + comp*i*x);
+      unsigned char *scratch = (unsigned char *) malloc(x*4);
+      fprintf(f, "#?RADIANCE\n# Written by stb_image_write.h\nFORMAT=32-bit_rle_rgbe\n"      );
+      fprintf(f, "EXPOSURE=          1.0000000000000\n\n-Y %d +X %d\n"                 , y, x);
+      for(i=0; i < y; i++)
+         stbiw__write_hdr_scanline(f, x, comp, scratch, data + comp*i*x);
       free(scratch);
       fclose(f);
    }
    return f != NULL;
 }
 
+/////////////////////////////////////////////////////////
+// PNG
+
 // stretchy buffer; stbiw__sbpush() == vector<>::push_back() -- stbiw__sbcount() == vector<>::size()
 #define stbiw__sbraw(a) ((int *) (a) - 2)
 #define stbiw__sbm(a)   stbiw__sbraw(a)[0]
@@ -666,6 +682,9 @@ int stbi_write_png(char const *filename, int x, int y, int comp, const void *dat
 
 /* Revision history
 
+      0.96 (2015-01-17)
+             add HDR output
+             fix monochrome BMP
       0.95 (2014-08-17)
 		       add monochrome TGA output
       0.94 (2014-05-31)