X-Git-Url: https://cads.iiap.res.in/gitview/?p=fits2jpeg.git;a=blobdiff_plain;f=src%2Fimage.c;h=f5f6c466394fac6ab4a855ae576497964b7a7083;hp=7a068e95892274491916e9ebca6027524081b3e6;hb=c217f20a424f31d11946263980a8f14ca7a79a0e;hpb=e31da38fa70e45758bd0c82b124c018c25e78e23 diff --git a/src/image.c b/src/image.c index 7a068e9..f5f6c46 100644 --- a/src/image.c +++ b/src/image.c @@ -24,8 +24,11 @@ /*Header Definitions*/ #include "fits2jpeg.h" -void scale_image(int scale, int npixels, - float *data, JSAMPLE *image_buffer) +/*---------------------------------------------------------------------------* + * SCALE_PIXELS: Changes the pixel scale to linear/log/sqroot/etc.. + *---------------------------------------------------------------------------*/ +void scale_pixels(int scale, unsigned int npixels, float *data, + JSAMPLE ** image_buffer) { unsigned int i = 0; int JMAXVAL = 255; @@ -34,7 +37,7 @@ void scale_image(int scale, int npixels, float scl_data = 0.0; - /* first find min & max in data */ + /* first find min & max in data */ datamax = -1.0 * FLT_MAX; datamin = FLT_MAX; for (i = 0; i < npixels; ++i) @@ -43,19 +46,22 @@ void scale_image(int scale, int npixels, if (data[i] < datamin) datamin = data[i]; } /*endfor*/ - /* Convert data into bytscaled values for jpeg file */ - /* the dynamic range is reduced to 255 for jpeg */ + + /* Convert data into bytscaled values for jpeg file */ + /* the dynamic range is reduced to 255 for jpeg */ scl_data = (datamax - datamin)/(float)JMAXVAL; + for (i = 0; i < npixels; ++i) data[i] = (data[i] - datamin)/scl_data; - /* All data is now squeezed into the range 0 - 255 */ - /* NOTE: At this point onwards min & max is 0 and 255 respectively */ + + /* All data is now squeezed into the range 0 - 255 */ + /* NOTE: At this point onwards min & max is 0 and 255 respectively */ datamax = (float)JMAXVAL; datamin = 0.0; - /* initialize image histogram. ensure all are zeroes in hist[] */ - /*-------------------------------------------------------------------*/ + /* initialize image histogram. ensure all are zeroes in hist[] */ + /*-----------------------------------------------------------------------*/ for (i = 0; i <= JMAXVAL; ++i) hist[i] = 0; /* construct the image histogram */ @@ -68,12 +74,16 @@ void scale_image(int scale, 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 - * if we dont generate image_buffer here, histo-eq will fail */ + * 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]); - /*-------------------------------------------------------------------*/ + /*-----------------------------------------------------------------------*/ switch (scale) @@ -82,28 +92,28 @@ void scale_image(int scale, 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 : @@ -135,12 +145,13 @@ void scale_image(int scale, 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] - datamin)/scl_data); + (*image_buffer)[i] = (int) abs(((*image_buffer)[i] + - datamin)/scl_data); } break; @@ -148,11 +159,73 @@ void scale_image(int scale, int npixels, /* histogram equalization */ printinfo("Performing Histogram Equalization"); for (i = 0; i < npixels; ++i) - image_buffer[i] = cumhist[image_buffer[i]] * 255; + (*image_buffer)[i] = cumhist[(*image_buffer)[i]] * JMAXVAL; break; default : printinfo("Using linear scale"); break; } +} + +/*---------------------------------------------------------------------------* + * 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) +{ + int offset = 0, index = 0; + int A, B, C, D, x, y, gray; + JSAMPLE *buff; + unsigned int i = 0, j = 0; + unsigned long npixels = 0; + long w = *xdim, h = *ydim; + long zxdim = 0, zydim = 0; + float xdiff, ydiff, xratio, yratio; + + zxdim = (int)(w * zoomfact); + zydim = (int)(h * zoomfact); + + npixels= zxdim * zydim; + + xratio = ((float)(w - 1))/zxdim; + yratio = ((float)(h - 1))/zydim; + /* allocate space for *buff */ + buff = malloc(sizeof(unsigned char) * zxdim * zydim); + + index = 0; + offset = 0; + for (i = 0; i < zydim; i++) + { + y = (int)(yratio * i); + ydiff = (yratio * i) - y; + + for (j = 0; j < zxdim; j++) + { + x = (int)(xratio * j); + + 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; + + gray = (int)(A * (1 - xdiff) * (1 - ydiff) + + B * (xdiff) * (1 - ydiff) + + C * (ydiff) * (1 - xdiff) + + D * (xdiff) * (ydiff) + ); + buff[offset++] = gray; + } + } + *xdim = zxdim; + *ydim = zydim; + (*image_buffer) = realloc((*image_buffer), sizeof(unsigned char) * npixels); + for (i = 0; i < npixels; ++i) + (*image_buffer)[i] = buff[i]; + free(buff); }