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