Initial Contribution

1 files changed, 275 insertions, 0 deletions

diff --git a/loadpng.c b/loadpng.c
new file mode 100644
index 0000000..b5c7a37
--- /dev/null
+++ b/loadpng.c
@@ -0,0 +1,275 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <png.h>
+
+#if 0
+#define LOG(x...) fprintf(stderr,"error: " x)
+#else
+#define LOG(x...) do {} while (0)
+#endif
+
+void *loadpng(const char *fn, unsigned *_width, unsigned *_height)
+{
+    FILE *fp = 0;
+    unsigned char header[8];
+    unsigned char *data = 0;
+    unsigned char **rowptrs = 0;
+    png_structp p = 0;
+    png_infop pi = 0;
+    
+    png_uint_32 width, height;
+    int bitdepth, colortype, imethod, cmethod, fmethod, i;
+
+    p = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
+    if(p == 0) {
+        LOG("%s: failed to allocate png read struct\n", fn);
+        return 0;
+    }
+
+    pi = png_create_info_struct(p);
+    if(pi == 0) {
+        LOG("%s: failed to allocate png info struct\n", fn);
+        goto oops;
+    }
+        
+    fp = fopen(fn, "rb");
+    if(fp == 0) {
+        LOG("%s: failed to open file\n", fn);
+        return 0;
+    }
+
+    if(fread(header, 8, 1, fp) != 1) {
+        LOG("%s: failed to read header\n", fn);
+        goto oops;
+    }
+    
+    if(png_sig_cmp(header, 0, 8)) {
+        LOG("%s: header is not a PNG header\n", fn);
+        goto oops;
+    }
+
+    if(setjmp(png_jmpbuf(p))) {
+        LOG("%s: png library error\n", fn);
+    oops:
+        png_destroy_read_struct(&p, &pi, 0);
+        if(fp != 0) fclose(fp);
+        if(data != 0) free(data);
+        if(rowptrs != 0) free(rowptrs);
+        return 0;
+    }
+
+    png_init_io(p, fp);
+    png_set_sig_bytes(p, 8);
+
+    png_read_info(p, pi);
+
+    png_get_IHDR(p, pi, &width, &height, &bitdepth, &colortype,
+                 &imethod, &cmethod, &fmethod);
+//    printf("PNG: %d x %d (d=%d, c=%d)\n",
+//           width, height, bitdepth, colortype);
+
+    switch(colortype){
+    case PNG_COLOR_TYPE_PALETTE:
+        png_set_palette_to_rgb(p);
+        break;
+
+    case PNG_COLOR_TYPE_RGB:
+        if(png_get_valid(p, pi, PNG_INFO_tRNS)) {
+            png_set_tRNS_to_alpha(p);
+        } else {
+            png_set_filler(p, 0xff, PNG_FILLER_AFTER);
+        }
+        break;
+        
+    case PNG_COLOR_TYPE_RGB_ALPHA:
+        break;
+
+    case PNG_COLOR_TYPE_GRAY:
+        if(bitdepth < 8) {
+            png_set_gray_1_2_4_to_8(p);
+        }
+        
+    default:
+        LOG("%s: unsupported (grayscale?) color type\n");
+        goto oops;
+    }
+
+    if(bitdepth == 16) {
+        png_set_strip_16(p);
+    }
+
+    data = (unsigned char*) malloc((width * 4) * height);
+    rowptrs = (unsigned char **) malloc(sizeof(unsigned char*) * height);
+
+    if((data == 0) || (rowptrs == 0)){
+        LOG("could not allocate data buffer\n");
+        goto oops;
+    }
+
+    for(i = 0; i < height; i++) {
+        rowptrs[i] = data + ((width * 4) * i);
+    }
+    
+    png_read_image(p, rowptrs);
+    
+    png_destroy_read_struct(&p, &pi, 0);
+    fclose(fp);
+    if(rowptrs != 0) free(rowptrs);
+
+    *_width = width;
+    *_height = height;
+    
+    return (void*) data;    
+}
+
+
+typedef struct
+{
+    const unsigned char*  base;
+    const unsigned char*  end;
+    const unsigned char*  cursor;
+
+} PngReader;
+
+static void
+png_reader_read_data( png_structp  png_ptr,
+                      png_bytep   data,
+                      png_size_t  length )
+{
+  PngReader* reader = png_get_io_ptr(png_ptr);
+  png_size_t avail  = (png_size_t)(reader->end - reader->cursor);
+
+  if (avail > length)
+      avail = length;
+
+  memcpy( data, reader->cursor, avail );
+  reader->cursor += avail;
+}
+
+
+void *readpng(const unsigned char *base, size_t   size, unsigned *_width, unsigned *_height)
+{
+    PngReader  reader;
+    unsigned char *data = 0;
+    unsigned char **rowptrs = 0;
+    png_structp p = 0;
+    png_infop pi = 0;
+
+    png_uint_32 width, height;
+    int bitdepth, colortype, imethod, cmethod, fmethod, i;
+
+    p = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
+    if(p == 0) {
+        LOG("%s: failed to allocate png read struct\n", fn);
+        return 0;
+    }
+
+    pi = png_create_info_struct(p);
+    if(pi == 0) {
+        LOG("%s: failed to allocate png info struct\n", fn);
+        goto oops;
+    }
+
+    reader.base   = base;
+    reader.end    = base + size;
+    reader.cursor = base;
+
+    if(size < 8 || png_sig_cmp(base, 0, 8)) {
+        LOG("%s: header is not a PNG header\n", fn);
+        goto oops;
+    }
+
+    reader.cursor += 8;
+
+    if(setjmp(png_jmpbuf(p))) {
+        LOG("%s: png library error\n", fn);
+    oops:
+        png_destroy_read_struct(&p, &pi, 0);
+        if(data != 0) free(data);
+        if(rowptrs != 0) free(rowptrs);
+        return 0;
+    }
+
+    png_set_read_fn (p, &reader, png_reader_read_data);
+    png_set_sig_bytes(p, 8);
+
+    png_read_info(p, pi);
+
+    png_get_IHDR(p, pi, &width, &height, &bitdepth, &colortype,
+                 &imethod, &cmethod, &fmethod);
+//    printf("PNG: %d x %d (d=%d, c=%d)\n",
+//           width, height, bitdepth, colortype);
+
+    switch(colortype){
+    case PNG_COLOR_TYPE_PALETTE:
+        png_set_palette_to_rgb(p);
+        break;
+
+    case PNG_COLOR_TYPE_RGB:
+        if(png_get_valid(p, pi, PNG_INFO_tRNS)) {
+            png_set_tRNS_to_alpha(p);
+        } else {
+            png_set_filler(p, 0xff, PNG_FILLER_AFTER);
+        }
+        break;
+
+    case PNG_COLOR_TYPE_RGB_ALPHA:
+        break;
+
+    case PNG_COLOR_TYPE_GRAY:
+        if(bitdepth < 8) {
+            png_set_gray_1_2_4_to_8(p);
+        }
+
+    default:
+        LOG("%s: unsupported (grayscale?) color type\n");
+        goto oops;
+    }
+
+    if(bitdepth == 16) {
+        png_set_strip_16(p);
+    }
+
+    data    = (unsigned char*) malloc((width * 4) * height);
+    rowptrs = (unsigned char **) malloc(sizeof(unsigned char*) * height);
+
+    if((data == 0) || (rowptrs == 0)){
+        LOG("could not allocate data buffer\n");
+        goto oops;
+    }
+
+    for(i = 0; i < height; i++) {
+        rowptrs[i] = data + ((width * 4) * i);
+    }
+
+    png_read_image(p, rowptrs);
+
+    png_destroy_read_struct(&p, &pi, 0);
+    if(rowptrs != 0) free(rowptrs);
+
+    *_width = width;
+    *_height = height;
+
+    return (void*) data;    
+}
+
+
+#if 0
+int main(int argc, char **argv)
+{
+    unsigned w,h;
+    unsigned char *data;
+    
+    if(argc < 2) return 0;
+
+
+    data = loadpng(argv[1], &w, &h);
+
+    if(data != 0) {
+        printf("w: %d  h: %d\n", w, h);
+    }
+
+    return 0;
+}
+#endif