X-Git-Url: https://cads.iiap.res.in/gitview/?p=fits2jpeg.git;a=blobdiff_plain;f=src%2Fimage.c;fp=src%2Fimage.c;h=f5f6c466394fac6ab4a855ae576497964b7a7083;hp=d1c22f07bfa79d885c512505d8258a5dc1eff96e;hb=c217f20a424f31d11946263980a8f14ca7a79a0e;hpb=60d065b23a2bdd48da5b8ef3ce591b7b0313c979

diff --git a/src/image.c b/src/image.c
index d1c22f0..f5f6c46 100644
--- a/src/image.c
+++ b/src/image.c
@@ -27,8 +27,8 @@
 /*---------------------------------------------------------------------------*
  * SCALE_PIXELS: Changes the pixel scale to linear/log/sqroot/etc..
  *---------------------------------------------------------------------------*/
-void scale_pixels(int scale, unsigned int npixels,
-                 float *data, JSAMPLE *image_buffer)
+void scale_pixels(int scale, unsigned int npixels, float *data,
+                 JSAMPLE ** image_buffer)
 {
     unsigned int i = 0;
     int JMAXVAL = 255;
@@ -74,10 +74,14 @@ void scale_pixels(int scale, unsigned int npixels,
     for (i = 1; i <= JMAXVAL; ++i)
         cumhist[i] += cumhist[i - 1] + hist[i];
 
+    /* Allocate image buffer */
+    (*image_buffer) = malloc(sizeof(unsigned char) * npixels);
+
+
     /* Linear scale (min-max) : This is the default scaling
      * histo-eq will fail if we dont generate image_buffer here              */
     for (i = 0; i < npixels; ++i)
-        image_buffer[i] = (int)(data[i]);
+        (*image_buffer)[i] = (int)(data[i]);
 
     /*-----------------------------------------------------------------------*/
 
@@ -88,28 +92,28 @@ void scale_pixels(int scale, unsigned int npixels,
             printinfo("Using square-root scale");
             scl_data = sqrt((float)JMAXVAL)/(float)JMAXVAL;
             for (i = 0; i < npixels; ++i)
-                image_buffer[i] = (int)(sqrt(data[i])/scl_data);
+                (*image_buffer)[i] = (int)(sqrt(data[i])/scl_data);
             break;
 
         case 2 :                                                   /* Square */
             printinfo("Using quadratic scale");
             scl_data = pow((float)JMAXVAL,2)/(float)JMAXVAL;
             for (i = 0; i < npixels; ++i)
-                image_buffer[i] = (int)abs((pow(data[i],2) - 1.0)/scl_data);
+                (*image_buffer)[i] = (int)abs((pow(data[i],2) - 1.0)/scl_data);
             break;
 
         case 3 :                                                    /* Cubic */
             printinfo("Using cubic scale");
             scl_data = pow((float)JMAXVAL,3)/(float)JMAXVAL;
             for (i = 0; i < npixels; ++i)
-                image_buffer[i] = (int)abs((pow(data[i],3) - 1.0)/scl_data);
+                (*image_buffer)[i] = (int)abs((pow(data[i],3) - 1.0)/scl_data);
             break;
 
         case 4 :                                                      /* log */
             printinfo("Using log scale");
             scl_data = log(1.0 + (float)JMAXVAL)/(float)JMAXVAL;
             for (i = 0; i < npixels; ++i)
-                image_buffer[i] = (int)((log(abs(data[i]) + 1.0))/scl_data);
+                (*image_buffer)[i] = (int)((log(abs(data[i]) + 1.0))/scl_data);
             break;
 
         case 5 :
@@ -141,12 +145,12 @@ void scale_pixels(int scale, unsigned int npixels,
             scl_data = (datamax - datamin)/(float)JMAXVAL;
             for (i = 0; i < npixels; ++i)
             {
-                if (image_buffer[i] >= datamax)
-                    image_buffer[i] = JMAXVAL;
-                else if (image_buffer[i] <= datamin)
-                    image_buffer[i] = 0;
+                if ((*image_buffer)[i] >= datamax)
+                    (*image_buffer)[i] = JMAXVAL;
+                else if ((*image_buffer)[i] <= datamin)
+                    (*image_buffer)[i] = 0;
                 else
-                    image_buffer[i] = (int) abs((image_buffer[i]
+                    (*image_buffer)[i] = (int) abs(((*image_buffer)[i]
                                     - datamin)/scl_data);
             }
             break;
@@ -155,19 +159,21 @@ void scale_pixels(int scale, unsigned int npixels,
             /* histogram equalization */
             printinfo("Performing Histogram Equalization");
             for (i = 0; i <  npixels; ++i)
-                image_buffer[i] = cumhist[image_buffer[i]] * JMAXVAL;
+                (*image_buffer)[i] = cumhist[(*image_buffer)[i]] * JMAXVAL;
             break;
         default :
             printinfo("Using linear scale");
             break;
     }
-
 }
 
 /*---------------------------------------------------------------------------*
- * RESIZE_IMAGE: Scales down/up the image_buffer
+ * RESIZE_IMAGE: Scales down/up the image_buffer using bilinear scaling
+ * Based on an article by "John" at
+ * http://tech-algorithm.com/articles/bilinear-image-scaling/
  *---------------------------------------------------------------------------*/
-void resize_image(long *xdim, long *ydim, float zoomfact, JSAMPLE *image_buffer)
+void resize_image(long *xdim, long *ydim, float zoomfact,
+                  JSAMPLE ** image_buffer)
 {
     int offset = 0, index = 0;
     int A, B, C, D, x, y, gray;
@@ -186,8 +192,8 @@ void resize_image(long *xdim, long *ydim, float zoomfact, JSAMPLE *image_buffer)
     xratio = ((float)(w - 1))/zxdim;
     yratio = ((float)(h - 1))/zydim;
 
-                                     /* allocate space for *buff */
-    buff   = (unsigned char *) malloc(sizeof(char) * zxdim * zydim);
+                            /* allocate space for *buff */
+    buff   = malloc(sizeof(unsigned char) * zxdim * zydim);
 
     index  = 0;
     offset = 0;
@@ -203,10 +209,10 @@ void resize_image(long *xdim, long *ydim, float zoomfact, JSAMPLE *image_buffer)
             xdiff = (xratio * j) - x;
             index = y * w + x;
 
-            A = image_buffer[index]         & 0xff;
-            B = image_buffer[index + 1]     & 0xff;
-            C = image_buffer[index + w]     & 0xff;
-            D = image_buffer[index + w + 1] & 0xff;
+            A = (*image_buffer)[index]         & 0xff;
+            B = (*image_buffer)[index + 1]     & 0xff;
+            C = (*image_buffer)[index + w]     & 0xff;
+            D = (*image_buffer)[index + w + 1] & 0xff;
 
             gray = (int)(A * (1 - xdiff) * (1 - ydiff)
                  +       B * (xdiff)     * (1 - ydiff)
@@ -218,10 +224,8 @@ void resize_image(long *xdim, long *ydim, float zoomfact, JSAMPLE *image_buffer)
     }
     *xdim = zxdim;
     *ydim = zydim;
-    image_buffer = realloc(image_buffer, sizeof(char) * npixels);
-    if (!image_buffer)
-        printerro("Failed to allocate memory");
-
+    (*image_buffer) = realloc((*image_buffer), sizeof(unsigned char) * npixels);
     for (i = 0; i <  npixels; ++i)
-        image_buffer[i] = buff[i];
+        (*image_buffer)[i] = buff[i];
+    free(buff);
 }