Add screen::unpackPNG()

libs/core/Makefile

@@ -20,7 +20,7 @@ DEPS = $(PXT_HEADERS) package.json Makefile Makefile.inc
 all: $(EXE)
 
 $(EXE): $(PXT_OBJS)
-	$(LD) -o $(EXE) $(LDFLAGS) -Wl,-Map,$(EXE:.elf=.map) $(PXT_OBJS) $(LIBSTDCPP) -lm -lpthread $(NPM_LIBS)
+	$(LD) -o $(EXE) $(LDFLAGS) -Wl,-Map,$(EXE:.elf=.map) $(PXT_OBJS) $(LIBSTDCPP) -lm -lpthread -lz $(NPM_LIBS)
 	cp $(EXE) $(EXE:.elf=.full)
 	$(PREF)strip $(EXE)
 	node -p 'require("fs").readFileSync("$(EXE)").toString("hex")' > $(HEX)

libs/core/_locales/core-jsdoc-strings.json

@@ -85,6 +85,7 @@
   "screen.setPixel|param|on": "a value indicating if the pixel should be on or off",
   "screen.setPixel|param|x": "the starting position's x coordinate, eg: 0",
   "screen.setPixel|param|y": "the starting position's x coordinate, eg: 0",
+  "screen.unpackPNG": "Decompresses a 1-bit gray scale PNG image to icon format.",
   "serial": "Reading and writing data over a serial connection.",
   "serial.writeDmesg": "Send DMESG debug buffer over serial."
 }

libs/core/png.cpp

@@ -0,0 +1,130 @@
+#include "pxt.h"
+#include "ev3const.h"
+#include <zlib.h>
+#include <stdlib.h>
+
+struct PNGHeader {
+    uint8_t pngHeader[8];
+    uint32_t lenIHDR;
+    uint8_t IHDR[4];
+    uint32_t width;
+    uint32_t height;
+    uint8_t bitDepth;
+    uint8_t colorType;
+    uint8_t compressionMethod;
+    uint8_t filterMethod;
+    uint8_t interlaceMethod;
+    uint32_t hdCRC;
+    uint32_t lenIDAT;
+    uint8_t IDAT[4];
+} __attribute__((packed));
+
+namespace screen {
+
+static uint32_t swap(uint32_t num) {
+    return ((num >> 24) & 0xff) | ((num << 8) & 0xff0000) | ((num >> 8) & 0xff00) |
+           ((num << 24) & 0xff000000);
+}
+
+static uint8_t revbits(uint8_t v) {
+    v = (v & 0xf0) >> 4 | (v & 0x0f) << 4;
+    v = (v & 0xcc) >> 2 | (v & 0x33) << 2;
+    v = (v & 0xaa) >> 1 | (v & 0x55) << 1;
+    return v;
+}
+
+/** Decompresses a 1-bit gray scale PNG image to icon format. */
+//%
+Buffer unpackPNG(Buffer png) {
+    if (!png) {
+        DMESG("PNG: Missing image");
+        return NULL;
+    }
+    if (png->length < sizeof(PNGHeader) + 4) {
+        DMESG("PNG: File too small");
+        return NULL;
+    }
+
+    if (memcmp(png->data, "\x89PNG\r\n\x1A\n", 8) != 0) {
+        DMESG("PNG: Invalid header");
+        return NULL;
+    }
+
+    struct PNGHeader hd;
+    memcpy(&hd, png->data, sizeof(hd));
+
+    if (memcmp(hd.IHDR, "IHDR", 4) != 0) {
+        DMESG("PNG: missing IHDR");
+        return NULL;
+    }
+
+    hd.lenIHDR = swap(hd.lenIHDR);
+    hd.width = swap(hd.width);
+    hd.height = swap(hd.height);
+    hd.lenIDAT = swap(hd.lenIDAT);
+
+    if (hd.lenIHDR != 13) {
+        DMESG("PNG: bad IHDR len");
+        return NULL;
+    }
+    if (hd.bitDepth != 1 || hd.colorType != 0 || hd.compressionMethod != 0 ||
+        hd.filterMethod != 0 || hd.interlaceMethod != 0) {
+        DMESG("PNG: not 1-bit grayscale");
+        return NULL;
+    }
+    if (memcmp(hd.IDAT, "IDAT", 4) != 0) {
+        DMESG("PNG: missing IDAT");
+        return NULL;
+    }
+    if (hd.lenIDAT + sizeof(hd) >= png->length) {
+        DMESG("PNG: buffer too short");
+        return NULL;
+    }
+    if (hd.width > 300 || hd.height > 300) {
+        DMESG("PNG: too big");
+        return NULL;
+    }
+
+    uint32_t byteW = (hd.width + 7) >> 3;
+    uint32_t expSize = (byteW + 1) * hd.height;
+    unsigned long sz = expSize;
+    uint8_t *tmp = (uint8_t *)malloc(sz);
+    int code = uncompress(tmp, &sz, png->data + sizeof(hd), hd.lenIDAT);
+    if (code != 0) {
+        DMESG("PNG: zlib failed: %d", code);
+        free(tmp);
+        return NULL;
+    }
+    if (sz != expSize) {
+        DMESG("PNG: invalid compressed size");
+        free(tmp);
+        return NULL;
+    }
+
+    Buffer res = mkBuffer(NULL, 2 + byteW * hd.height);
+    res->data[0] = 0xf0;
+    res->data[1] = hd.width;
+    uint8_t *dst = res->data + 2;
+    uint8_t *src = tmp;
+    uint8_t lastMask = (1 << (hd.width & 7)) - 1;
+    if (lastMask == 0)
+        lastMask = 0xff;
+    for (uint32_t i = 0; i < hd.height; ++i) {
+        if (*src++ != 0) {
+            DMESG("PNG: unsupported filter");
+            free(tmp);
+            decrRC(res);
+            return NULL;
+        }
+        for (uint32_t j = 0; j < byteW; ++j) {
+            *dst = ~revbits(*src++);
+            if (j == byteW - 1) {
+                *dst &= lastMask;
+            }
+            dst++;
+        }
+    }
+    free(tmp);
+    return res;
+}
+}

libs/core/pxt.json

@@ -11,6 +11,7 @@
         "mmap.cpp",
         "control.cpp",
         "buttons.ts",
+        "png.cpp",
         "screen.cpp",
         "screen.ts",
         "output.cpp",

libs/core/shims.d.ts

@@ -70,6 +70,12 @@ declare namespace serial {
     //% shim=serial::writeDmesg
     function writeDmesg(): void;
 }
+declare namespace screen {
+
+    /** Decompresses a 1-bit gray scale PNG image to icon format. */
+    //% shim=screen::unpackPNG
+    function unpackPNG(png: Buffer): Buffer;
+}
 declare namespace screen {
 
     /** Double size of an icon. */

pxtarget.json

@@ -62,7 +62,7 @@
     },
     "compileService": {
         "buildEngine": "dockermake",
-        "dockerImage": "pext/ev3",
+        "dockerImage": "pext/ev3:zlib",
         "serviceId": "ev3"
     },
     "appTheme": {