[ESP32] ESP32でGIFを軽量GIFデコーダでデコードする

まず…なぜGIFなのか?

「esp32とTFT液晶で強震モニタを作りたい」

を前提に色々試行錯誤しています。前のTTSの記事もその一環です。強震モニタとはリアルタイムで緊急地震速報(予報も含める)を見ることができるアレです。

www.kmoni.bosai.go.jp

強震モニタ

http://www.kmoni.bosai.go.jp

webページを分析してみると

リアルタイムにGIFファイルをDLしてを重ねて表示しているようです。なのでGIFファイルを表示する必要があるのです。

ESP32でTFT液晶(ILI9486)を使う準備

ILI9486である必要はありませんが、TFT液晶を使うとなるとライブラリが必須になります。

TFT液晶用のライブラリは何個か候補があります。僕が渡り歩いたのは下の3つです。

Adafruit-GFX-Library

GitHub

GitHub - adafruit/Adafruit-GFX-Library: Adafruit GFX graphics core library, t...

https://github.com/adafruit/Adafruit-GFX-Library

Adafruit GFX graphics core library, this is the 'core' class that all our other graphics libraries derive from - GitHub - adafruit/Adafruit-GFX-Library: Adafruit GFX graphics core library, ...

TFT_eSPI

GitHub

GitHub - Bodmer/TFT_eSPI: Arduino and PlatformIO IDE compatible TFT library o...

https://github.com/Bodmer/TFT_eSPI

Arduino and PlatformIO IDE compatible TFT library optimised for the Raspberry Pi Pico (RP2040), STM32, ESP8266 and ESP32 that supports different driver chips - GitHub - Bodmer/TFT_eSPI: Arduino and...

LovyanGFX

GitHub

GitHub - lovyan03/LovyanGFX: SPI LCD graphics library for ESP32 (ESP-IDF/Ardu...

https://github.com/lovyan03/LovyanGFX

SPI LCD graphics library for ESP32 (ESP-IDF/ArduinoESP32) / ESP8266 (ArduinoESP8266) / SAMD51(Seeed ArduinoSAMD51) - GitHub - lovyan03/LovyanGFX: SPI LCD graphics library for ESP32 (ESP-IDF/Arduino...

この中で一番高機能、しかも日本人なら、LovyanGFX一択です！！開発者の「らびやん」さんは日本人でリファレンスも多くあり高性能なライブラリです。書き出し時に拡大・縮小ができたり、日本語出力が標準でできたり(これは便利!!)、海外ライブラリにはない便利なことができて大変助かりました。Adafruitの謹製ライブラリは速度面で遅いイメージ、TFT_eSPIも高機能ですが、日本語出力なんて海外ライブラリにあるわけもなく…リファレンスを読むと

最初からLovyanGFX使っとけばよかったOTL

基本的な命令は標準ライブラリやTFT_eSPTと同じメソッドですのですんなり移行できます。

Lang-ship

LovyanGFX入門その1 基本描画系

https://lang-ship.com/blog/work/lovyangfx-1/

概要らびやんさん作のLovyanGFXを、自作M5Liteライブラリなどで利用させていただいていますが、描画系の解説用として、LovyanGFXの使い方を確認しなおしたいと思います。上記にまとめた資料が置いてあります。LovyanGFXとは

esp32との接続やデモの表示の例はたくさんありますので、そちらを参考に画面表示できるまでしときます。これができないとデコードしても表示までたどり着けません。

GIFのデコーダーを探しまくる

LovyanGFXではJPEGはlcd.drawJpgFileですぐ表示できるようです。TJpg_Decoderとかでデコードしてたのは何だったんだろうと思ってしまいます。

GIFもデコーダあるのかなぁ(ﾜｸﾜｸ

チーン。AnimatedGIFを使いましょうということですね。

らびやんさんが言うなら間違いないです！AnimatedGIFのリファレンスを読んでみました。結構、機能満載なライブラリでして、

もっとGIFファイル(静止画)をサッとデコードできそうな簡単なライブラリはないかなぁ～(贅沢

と探してはみたんですけど意外にないんですねwで、見つけた記事が

blog.boochow.com

https://blog.boochow.com/article/428487132.html

です。この記事を書いた人も軽量デコーダーを探していました。なんと下の方にシンプルなデコーダのソースコードが載っているではないですか。

GIFデコーダの改良

さきほどの記事のデコーダを早速コピペして動かしたところ、GIFファイルが表示できません。というか、いろいろ試すと表示できるのもあればできないものもあります。よく調べてみるとinit_decoder()で負数が返ってきているようです。

これは…GIFファイルのヘッダをうまく読めてないようです。ヘッダを正しく読んでいないので透過GIFにも対応していないということになります。

さぁ～次いこー(棒

としましたが、あまりに探して見つからないので重い腰を上げることにしました。今考えると意地になってましたねw

GIFのヘッダの仕様書を読みながらライブラリを改良してみました。どうやらExtensionを正しく読んでいない様子。正しく読むようにして透過GIFへの対応をしました。長いですが下にコードを張ります

www.tohoho-web.com

GIFフォーマットの詳細 - とほほのWWW入門

https://www.tohoho-web.com/wwwgif.htm

    #ifndef __GIF_MODI_H__
    #define __GIF_MODI_H__

    //typedef void(*gif_draw_pixel_t)(unsigned char r, unsigned char g, unsigned char b);
    typedef void(*gif_draw_pixel_t)(unsigned char r, unsigned char g, unsigned char b , bool trans_gif , bool trans_pixel);

    typedef struct{
	    unsigned short SCREEN_WIDTH;
	    unsigned short SCREEN_HEIGHT;
	    unsigned char BYTE_5;
	    unsigned char BACKGROUND;
	    unsigned char ASPECT_RATIO;
    } SCREEN_DESC;

    typedef struct{
	    unsigned short LEFT;
	    unsigned short UP;
	    unsigned short IMAGE_WIDTH;
	    unsigned short IMAGE_HEIGHT;
	    unsigned char BYTE_9;
    } IMAGE_DESC;
    
	typedef struct{
		unsigned char BLOCK_SIZE;    //Block Size(1 Byte) 0x04固定
		unsigned char BYTE_2;        //Reserved(3 Bits),Disposal Mothod(3 Bits),User Input Flag(1 Bit),Transparent Color Flag(1 Bit)
		bool TC_FLAG;                //Transparent Color Flag(1 Bit)
		unsigned short DELAY_TIME;   //Delay Time(2 Bytes)
		unsigned char TC_INDEX;      //Transparent Color Index(1 Byte)
	} GC_EXTENTION;

    typedef struct{
	    unsigned char R;
	    unsigned char G;
	    unsigned char B;
    } COLOR;

    typedef struct{
	    SCREEN_DESC screenDesc;
	    IMAGE_DESC imageDesc;
    	GC_EXTENTION gcExtention;
    } GIF_IMAGE;

    typedef struct{
	    unsigned short code;
	    unsigned short prevCode;
	    unsigned short nextCode;
    } DICTIONARY_ENTRY;

    class GIF {
    	
	    private:
		    //unsigned char BUFFER[16];
		    unsigned char BUFFER[256];
		    unsigned short PrimaryCodeSize, PrimaryDictSize;
		    unsigned short currentCodeSize, currentDictSize;

		    unsigned short code, oldcode = 0;
		    unsigned short code1, code2;
		    unsigned short code_CLEAR, code_END;

		    COLOR g_GlobalColorTable[256];

		    #define MAX_DICT_SIZE 4098
		    DICTIONARY_ENTRY Dictionary[MAX_DICT_SIZE];
		    unsigned char bitsRemaining;
		    unsigned short getNextCode(void);
		    int checkSignature(char*);
		    File g_fileObject;
		    gif_draw_pixel_t gif_draw_pixel;

		    int read_file(File, unsigned char *, int);
		    unsigned char read_code;

		    unsigned char byte5;
		    unsigned char byte9;
		    unsigned char byte2; // Graphic Control Extension用追加
    	
    		bool trans_gif; 					//gif_draw_pixelへの引き渡し用
    		unsigned char trans_color_index;

		    unsigned char currentDataSectionLength;

	    public:
		    int init_decoder(File, GIF_IMAGE *);
		    int drawGIFImage(gif_draw_pixel_t);
		    unsigned char counter;
		    void GIFDrawPixel(unsigned char);
		    unsigned short imgWidth, imgHeight;
    };

#endif

#ifndef __GIF_MODI_H__

#define __GIF_MODI_H__

//typedef void(*gif_draw_pixel_t)(unsigned char r, unsigned char g, unsigned char b);

typedef void(*gif_draw_pixel_t)(unsigned char r, unsigned char g, unsigned char b , bool trans_gif , bool trans_pixel);

typedef struct{

unsigned short SCREEN_WIDTH;

unsigned short SCREEN_HEIGHT;

unsigned char BYTE_5;

unsigned char BACKGROUND;

unsigned char ASPECT_RATIO;

} SCREEN_DESC;

typedef struct{

unsigned short LEFT;

unsigned short UP;

unsigned short IMAGE_WIDTH;

unsigned short IMAGE_HEIGHT;

unsigned char BYTE_9;

} IMAGE_DESC;

typedef struct{

unsigned char BLOCK_SIZE; //Block Size(1 Byte) 0x04固定

unsigned char BYTE_2; //Reserved(3 Bits),Disposal Mothod(3 Bits),User Input Flag(1 Bit),Transparent Color Flag(1 Bit)

bool TC_FLAG; //Transparent Color Flag(1 Bit)

unsigned short DELAY_TIME; //Delay Time(2 Bytes)

unsigned char TC_INDEX; //Transparent Color Index(1 Byte)

} GC_EXTENTION;

typedef struct{

unsigned char R;

unsigned char G;

unsigned char B;

} COLOR;

typedef struct{

SCREEN_DESC screenDesc;

IMAGE_DESC imageDesc;

GC_EXTENTION gcExtention;

} GIF_IMAGE;

typedef struct{

unsigned short code;

unsigned short prevCode;

unsigned short nextCode;

} DICTIONARY_ENTRY;

class GIF {

private:

//unsigned char BUFFER[16];

unsigned char BUFFER[256];

unsigned short PrimaryCodeSize, PrimaryDictSize;

unsigned short currentCodeSize, currentDictSize;

unsigned short code, oldcode = 0;

unsigned short code1, code2;

unsigned short code_CLEAR, code_END;

COLOR g_GlobalColorTable[256];

#define MAX_DICT_SIZE 4098

DICTIONARY_ENTRY Dictionary[MAX_DICT_SIZE];

unsigned char bitsRemaining;

unsigned short getNextCode(void);

int checkSignature(char*);

File g_fileObject;

gif_draw_pixel_t gif_draw_pixel;

int read_file(File, unsigned char *, int);

unsigned char read_code;

unsigned char byte5;

unsigned char byte9;

unsigned char byte2; // Graphic Control Extension用追加

bool trans_gif; //gif_draw_pixelへの引き渡し用

unsigned char trans_color_index;

unsigned char currentDataSectionLength;

public:

int init_decoder(File, GIF_IMAGE *);

int drawGIFImage(gif_draw_pixel_t);

unsigned char counter;

void GIFDrawPixel(unsigned char);

unsigned short imgWidth, imgHeight;

};

#endif

#include <FS.h>
#include "gif_modi.h"

int GIF::init_decoder(File fileObject, GIF_IMAGE * gifImage) {
	unsigned int i;
	unsigned char bpp;
	unsigned short minLZWCodeLength;
	unsigned int GCT_size;

	g_fileObject = fileObject;

	for(int i=0 ; i < 16 ; i++) BUFFER[i] = 0; //バッファをリセットしないと再利用できない
	
	
	//GIF Headerの読み込み
	
	//Signature(3 Bytes) + Version(3 Bytes) "GIF89a" or "GIF87a"
	read_file(g_fileObject, BUFFER, 6);
	if (checkSignature((char*)BUFFER) != 1) return -1;
	
	read_file(g_fileObject, BUFFER, 7);
	
	//Logical Screen Width(2 Bytes)
	(*gifImage).screenDesc.SCREEN_WIDTH = (BUFFER[1] << 8) + BUFFER[0];
	
	//Logical Screen Height(2 Bytes)
	(*gifImage).screenDesc.SCREEN_HEIGHT = (BUFFER[3] << 8) + BUFFER[2];

	//Global Color Table Flag(1 Bit),Color Resolution(3 Bits),Sort Flag(1 Bit),Size of Global Color Table(3 Bits)
	(*gifImage).screenDesc.BYTE_5 = BUFFER[4];

	//Background Color Index(1 Byte)
	(*gifImage).screenDesc.BACKGROUND = BUFFER[5];
	
	//Pixel Aspect Ratio(1 Byte)
	(*gifImage).screenDesc.ASPECT_RATIO = BUFFER[6];

	byte5 = (*gifImage).screenDesc.BYTE_5;
	
	//Size of Global Color Table(3 Bits)
	bpp = (byte5 & 0x07);
	//2の(Size of Global Color Table)乗個のGlobal Color Tableがある
	GCT_size = 2 << bpp;

	//Global Color Table Flag(1 Bit)があるなら
	if (byte5 & 0x80){

		for (i = 0; i < GCT_size; i++){
			//1つの色情報につきRGBの3バイトずつ、GCT_size個読む
			read_file(g_fileObject, BUFFER, 3);
			g_GlobalColorTable[i].R = BUFFER[0];
			g_GlobalColorTable[i].G = BUFFER[1];
			g_GlobalColorTable[i].B = BUFFER[2];
		}
	}
	else return -1;

	//Image Separator(1B) = 0x2cが出るまでエクステンションを正しく読み飛ばす
	do {
		read_file(g_fileObject, BUFFER, 1);
		
		//Extensionコードがあるなら
		if (BUFFER[0] == 0x21){
			read_file(g_fileObject, BUFFER, 1);
			
			//Block: Graphic Control Extension
			if (BUFFER[0] == 0xf9){
				read_file(g_fileObject, BUFFER, 6);
				
				//Block Size(1 Byte) 0x04 固定値
				(*gifImage).gcExtention.BLOCK_SIZE = BUFFER[0];
				
				//Reserved(3 Bits),Disposal Mothod(3 Bits),User Input Flag(1 Bit),Transparent Color Flag(1 Bit)
				(*gifImage).gcExtention.BYTE_2 = BUFFER[1];
				byte2 = (*gifImage).gcExtention.BYTE_2;
				
				if(byte2 & 0x01){
					(*gifImage).gcExtention.TC_FLAG = true;
				}else{
					(*gifImage).gcExtention.TC_FLAG = false;
				}
				trans_gif = (*gifImage).gcExtention.TC_FLAG;
				
				//Delay Time(2 Bytes)
				(*gifImage).gcExtention.DELAY_TIME = (BUFFER[3] << 8) + BUFFER[2];
				
				//Transparent Color Index(1 Byte)
				(*gifImage).gcExtention.TC_INDEX = BUFFER[4];
				trans_color_index = (*gifImage).gcExtention.TC_INDEX;
			}
			
			//Block: Comment Extension
			if (BUFFER[0] == 0xfe){
				read_file(g_fileObject, BUFFER, 1);
				//unsigned char c_size = BUFFER[0];
				//read_file(g_fileObject, BUFFER, c_size);
				do{
					read_file(g_fileObject, BUFFER, 1);
				} while (BUFFER[0] != 0x00);
				continue;
			}
			
			//Block: Plain Text Extension
			if (BUFFER[0] == 0x01){
				read_file(g_fileObject, BUFFER, 13);
				read_file(g_fileObject, BUFFER, 1);
				//unsigned char t_size = BUFFER[0];
				//read_file(g_fileObject, BUFFER, t_size);
				do{
					read_file(g_fileObject, BUFFER, 1);
				} while (BUFFER[0] != 0x00);
				continue;

			}
			
			//Block: Application Extension
			if (BUFFER[0] == 0xff){
				read_file(g_fileObject, BUFFER, 12);
				read_file(g_fileObject, BUFFER, 1);
				//unsigned char a_size = BUFFER[0];
				//read_file(g_fileObject, BUFFER, a_size);
				do{
					read_file(g_fileObject, BUFFER, 1);
				} while (BUFFER[0] != 0x00);
				continue;
				
			}
			
		}
		
	} while (BUFFER[0] != 0x2C);

	
	//Block: Image Blockの読み込み
	read_file(g_fileObject, BUFFER, 11);

	//Image Left Position(2 Bytes)
	(*gifImage).imageDesc.LEFT = (BUFFER[1] << 8) + BUFFER[0];

	//Image Top Position(2 Bytes)
	(*gifImage).imageDesc.UP = (BUFFER[3] << 8) + BUFFER[2];
	
	//Image Width(2 Bytes)
	(*gifImage).imageDesc.IMAGE_WIDTH = (BUFFER[5] << 8) + BUFFER[4];
	
	//Image Height(2 Bytes)
	(*gifImage).imageDesc.IMAGE_HEIGHT = (BUFFER[7] << 8) + BUFFER[6];
	
	//Local Color Table Flag(1 Bit),Interlace Flag(1 Bit),Sort Flag(1 Bit),Reserved[未使用](2 Bits),Size of Local Color Table(3 Bits)
	(*gifImage).imageDesc.BYTE_9 = BUFFER[8];

	imgWidth = (*gifImage).imageDesc.IMAGE_WIDTH;
	imgHeight = (*gifImage).imageDesc.IMAGE_HEIGHT;
	byte9 = (*gifImage).imageDesc.BYTE_9;

	//LZW Minimum Code Side(1 Byte)
	minLZWCodeLength = BUFFER[9] + 1;
	
	//Block Size(1 Byte)
	currentDataSectionLength = BUFFER[10];

	code_CLEAR = GCT_size;
	code_END = GCT_size + 1;
	PrimaryDictSize = GCT_size + 2;
	PrimaryCodeSize = minLZWCodeLength;
	currentCodeSize = minLZWCodeLength;

	return 0;

}

int GIF::read_file(File fileObject, unsigned char *buf, int count){
  return fileObject.read(buf,count);
}

int GIF::drawGIFImage(gif_draw_pixel_t draw_pixel_func){
	unsigned int i;

	gif_draw_pixel = draw_pixel_func;
	currentDictSize = PrimaryDictSize;

	counter = 0;

	for (i = 0; i < MAX_DICT_SIZE; i++)
		Dictionary[i].prevCode = Dictionary[i].nextCode = 0;

	bitsRemaining = 0;

	while ((code = getNextCode()) != code_END){


		if (code == code_CLEAR){
			currentCodeSize = PrimaryCodeSize;
			currentDictSize = PrimaryDictSize;
			oldcode = getNextCode();

			if (oldcode > currentDictSize){
				return -3;
			}
			GIFDrawPixel(oldcode);
			continue;
		}


		if (code < currentDictSize){
			code1 = code;
			code2 = 0;

			while (code1 >= PrimaryDictSize){
				Dictionary[code1 - PrimaryDictSize].nextCode = code2;
				code2 = code1;
				code1 = Dictionary[code1 - PrimaryDictSize].prevCode;
				if (code1 >= code2)
					return -3;
			}

			GIFDrawPixel(code1);
			while (code2 != 0){
				GIFDrawPixel(Dictionary[code2 - PrimaryDictSize].code);
				code2 = Dictionary[code2 - PrimaryDictSize].nextCode;
			}
			Dictionary[currentDictSize - PrimaryDictSize].code = code1;
			Dictionary[currentDictSize - PrimaryDictSize].prevCode = oldcode;
			++currentDictSize;

			if (currentDictSize == MAX_DICT_SIZE) return -2;

			if ((currentDictSize) == (0x0001 << currentCodeSize))
				++currentCodeSize;
			if (currentCodeSize > 12)
				currentCodeSize = 12;

			oldcode = code;
		}
		else {
			code1 = oldcode;
			code2 = 0;

			while (code1 >= PrimaryDictSize){
				Dictionary[code1 - PrimaryDictSize].nextCode = code2;
				code2 = code1;
				code1 = Dictionary[code1 - PrimaryDictSize].prevCode;
				if (code1 >= code2)
					return -3;
			}

			GIFDrawPixel(code1);
			while (code2 != 0){
				GIFDrawPixel(Dictionary[code2 - PrimaryDictSize].code);
				code2 = Dictionary[code2 - PrimaryDictSize].nextCode;
			}
			GIFDrawPixel(code1);

			Dictionary[currentDictSize - PrimaryDictSize].code = code1;
			Dictionary[currentDictSize - PrimaryDictSize].prevCode = oldcode;
			++currentDictSize;
			//std::cout << "dictionary size: " << std::dec << currentDictSize << std::endl;

			if (currentDictSize == MAX_DICT_SIZE) return -2;


			if ((currentDictSize) == (0x0001 << currentCodeSize))
				++currentCodeSize;

			if (currentCodeSize > 12)
				currentCodeSize = 12;

			oldcode = code;
		}
	}
	return 0;
}


int GIF::checkSignature(char * IN){
	char signature[7];
	int i;

	for (i = 0; i <= 6; i++)
		signature[i] = IN[i];

	if ((strcmp(signature, "GIF87a") == 0) || (strcmp(signature, "GIF89a") == 0))
		return 1;
	else
		return 0;
}

unsigned short GIF::getNextCode(void){
	unsigned int retval = 0, temp;

	if (bitsRemaining >= currentCodeSize){
		retval = (read_code & ((0x01 << currentCodeSize) - 1));
		read_code >>= currentCodeSize;
		bitsRemaining -= currentCodeSize;
	}
	else {
		retval = (read_code & ((0x01 << bitsRemaining) - 1));
		read_file(g_fileObject, &read_code, 1);
		++counter;
		if (counter == currentDataSectionLength){
			counter = 0;
			read_file(g_fileObject, &currentDataSectionLength, 1);
		}

		if ((currentCodeSize - bitsRemaining) <= 8){
			temp = (read_code & ((0x01 << (currentCodeSize - bitsRemaining)) - 1));
			retval += (temp << bitsRemaining);
			read_code >>= (currentCodeSize - bitsRemaining);
			bitsRemaining = 8 - (currentCodeSize - bitsRemaining);
		}
		else {
			retval += (read_code << bitsRemaining);
			read_file(g_fileObject, &read_code, 1);
			++counter;
			if (counter == currentDataSectionLength){
				counter = 0;
				read_file(g_fileObject, &currentDataSectionLength, 1);
			}
			retval += ((read_code & ((0x01 << (currentCodeSize - bitsRemaining - 8)) - 1)) << (bitsRemaining + 8));
			read_code >>= (currentCodeSize - bitsRemaining - 8);
			bitsRemaining = 8 - (currentCodeSize - bitsRemaining - 8);
		}
	}
	return retval;
}

void GIF::GIFDrawPixel(unsigned char code){
	COLOR rgbColor;
	bool trans_pixel = false;

	rgbColor = g_GlobalColorTable[code];
	
	if(trans_gif && code == trans_color_index) trans_pixel = true;
	
	(*gif_draw_pixel)(rgbColor.R, rgbColor.G, rgbColor.B, trans_gif , trans_pixel);
}

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#include <FS.h>

#include "gif_modi.h"

int GIF::init_decoder(File fileObject, GIF_IMAGE * gifImage) {

unsigned int i;

unsigned char bpp;

unsigned short minLZWCodeLength;

unsigned int GCT_size;

g_fileObject = fileObject;

for(int i=0 ; i < 16 ; i++) BUFFER[i] = 0; //バッファをリセットしないと再利用できない

//GIF Headerの読み込み

//Signature(3 Bytes) + Version(3 Bytes) "GIF89a" or "GIF87a"

read_file(g_fileObject, BUFFER, 6);

if (checkSignature((char*)BUFFER) != 1) return -1;

read_file(g_fileObject, BUFFER, 7);

//Logical Screen Width(2 Bytes)

(*gifImage).screenDesc.SCREEN_WIDTH = (BUFFER[1] << 8) + BUFFER[0];

//Logical Screen Height(2 Bytes)

(*gifImage).screenDesc.SCREEN_HEIGHT = (BUFFER[3] << 8) + BUFFER[2];

//Global Color Table Flag(1 Bit),Color Resolution(3 Bits),Sort Flag(1 Bit),Size of Global Color Table(3 Bits)

(*gifImage).screenDesc.BYTE_5 = BUFFER[4];

//Background Color Index(1 Byte)

(*gifImage).screenDesc.BACKGROUND = BUFFER[5];

//Pixel Aspect Ratio(1 Byte)

(*gifImage).screenDesc.ASPECT_RATIO = BUFFER[6];

byte5 = (*gifImage).screenDesc.BYTE_5;

//Size of Global Color Table(3 Bits)

bpp = (byte5 & 0x07);

//2の(Size of Global Color Table)乗個のGlobal Color Tableがある

GCT_size = 2 << bpp;

//Global Color Table Flag(1 Bit)があるなら

if (byte5 & 0x80){

for (i = 0; i < GCT_size; i++){

//1つの色情報につきRGBの3バイトずつ、GCT_size個読む

read_file(g_fileObject, BUFFER, 3);

g_GlobalColorTable[i].R = BUFFER[0];

g_GlobalColorTable[i].G = BUFFER[1];

g_GlobalColorTable[i].B = BUFFER[2];

}

else return -1;

//Image Separator(1B) = 0x2cが出るまでエクステンションを正しく読み飛ばす

do {

read_file(g_fileObject, BUFFER, 1);

//Extensionコードがあるなら

if (BUFFER[0] == 0x21){

read_file(g_fileObject, BUFFER, 1);

//Block: Graphic Control Extension

if (BUFFER[0] == 0xf9){

read_file(g_fileObject, BUFFER, 6);

//Block Size(1 Byte) 0x04 固定値

(*gifImage).gcExtention.BLOCK_SIZE = BUFFER[0];

//Reserved(3 Bits),Disposal Mothod(3 Bits),User Input Flag(1 Bit),Transparent Color Flag(1 Bit)

(*gifImage).gcExtention.BYTE_2 = BUFFER[1];

byte2 = (*gifImage).gcExtention.BYTE_2;

if(byte2 & 0x01){

(*gifImage).gcExtention.TC_FLAG = true;

}else{

(*gifImage).gcExtention.TC_FLAG = false;

}

trans_gif = (*gifImage).gcExtention.TC_FLAG;

//Delay Time(2 Bytes)

(*gifImage).gcExtention.DELAY_TIME = (BUFFER[3] << 8) + BUFFER[2];

//Transparent Color Index(1 Byte)

(*gifImage).gcExtention.TC_INDEX = BUFFER[4];

trans_color_index = (*gifImage).gcExtention.TC_INDEX;

}

//Block: Comment Extension

if (BUFFER[0] == 0xfe){

read_file(g_fileObject, BUFFER, 1);

//unsigned char c_size = BUFFER[0];

//read_file(g_fileObject, BUFFER, c_size);

do{

read_file(g_fileObject, BUFFER, 1);

} while (BUFFER[0] != 0x00);

continue;

}

//Block: Plain Text Extension

if (BUFFER[0] == 0x01){

read_file(g_fileObject, BUFFER, 13);

read_file(g_fileObject, BUFFER, 1);

//unsigned char t_size = BUFFER[0];

//read_file(g_fileObject, BUFFER, t_size);

do{

read_file(g_fileObject, BUFFER, 1);

} while (BUFFER[0] != 0x00);

continue;

}

//Block: Application Extension

if (BUFFER[0] == 0xff){

read_file(g_fileObject, BUFFER, 12);

read_file(g_fileObject, BUFFER, 1);

//unsigned char a_size = BUFFER[0];

//read_file(g_fileObject, BUFFER, a_size);

do{

read_file(g_fileObject, BUFFER, 1);

} while (BUFFER[0] != 0x00);

continue;

}

} while (BUFFER[0] != 0x2C);

//Block: Image Blockの読み込み

read_file(g_fileObject, BUFFER, 11);

//Image Left Position(2 Bytes)

(*gifImage).imageDesc.LEFT = (BUFFER[1] << 8) + BUFFER[0];

//Image Top Position(2 Bytes)

(*gifImage).imageDesc.UP = (BUFFER[3] << 8) + BUFFER[2];

//Image Width(2 Bytes)

(*gifImage).imageDesc.IMAGE_WIDTH = (BUFFER[5] << 8) + BUFFER[4];

//Image Height(2 Bytes)

(*gifImage).imageDesc.IMAGE_HEIGHT = (BUFFER[7] << 8) + BUFFER[6];

//Local Color Table Flag(1 Bit),Interlace Flag(1 Bit),Sort Flag(1 Bit),Reserved[未使用](2 Bits),Size of Local Color Table(3 Bits)

(*gifImage).imageDesc.BYTE_9 = BUFFER[8];

imgWidth = (*gifImage).imageDesc.IMAGE_WIDTH;

imgHeight = (*gifImage).imageDesc.IMAGE_HEIGHT;

byte9 = (*gifImage).imageDesc.BYTE_9;

//LZW Minimum Code Side(1 Byte)

minLZWCodeLength = BUFFER[9] + 1;

//Block Size(1 Byte)

currentDataSectionLength = BUFFER[10];

code_CLEAR = GCT_size;

code_END = GCT_size + 1;

PrimaryDictSize = GCT_size + 2;

PrimaryCodeSize = minLZWCodeLength;

currentCodeSize = minLZWCodeLength;

return 0;

}

int GIF::read_file(File fileObject, unsigned char *buf, int count){

return fileObject.read(buf,count);

}

int GIF::drawGIFImage(gif_draw_pixel_t draw_pixel_func){

unsigned int i;

gif_draw_pixel = draw_pixel_func;

currentDictSize = PrimaryDictSize;

counter = 0;

for (i = 0; i < MAX_DICT_SIZE; i++)

Dictionary[i].prevCode = Dictionary[i].nextCode = 0;

bitsRemaining = 0;

while ((code = getNextCode()) != code_END){

if (code == code_CLEAR){

currentCodeSize = PrimaryCodeSize;

currentDictSize = PrimaryDictSize;

oldcode = getNextCode();

if (oldcode > currentDictSize){

return -3;

}

GIFDrawPixel(oldcode);

continue;

}

if (code < currentDictSize){

code1 = code;

code2 = 0;

while (code1 >= PrimaryDictSize){

Dictionary[code1 - PrimaryDictSize].nextCode = code2;

code2 = code1;

code1 = Dictionary[code1 - PrimaryDictSize].prevCode;

if (code1 >= code2)

return -3;

}

GIFDrawPixel(code1);

while (code2 != 0){

GIFDrawPixel(Dictionary[code2 - PrimaryDictSize].code);

code2 = Dictionary[code2 - PrimaryDictSize].nextCode;

}

Dictionary[currentDictSize - PrimaryDictSize].code = code1;

Dictionary[currentDictSize - PrimaryDictSize].prevCode = oldcode;

++currentDictSize;

if (currentDictSize == MAX_DICT_SIZE) return -2;

if ((currentDictSize) == (0x0001 << currentCodeSize))

++currentCodeSize;

if (currentCodeSize > 12)

currentCodeSize = 12;

oldcode = code;

}

else {

code1 = oldcode;

code2 = 0;

while (code1 >= PrimaryDictSize){

Dictionary[code1 - PrimaryDictSize].nextCode = code2;

code2 = code1;

code1 = Dictionary[code1 - PrimaryDictSize].prevCode;

if (code1 >= code2)

return -3;

}

GIFDrawPixel(code1);

while (code2 != 0){

GIFDrawPixel(Dictionary[code2 - PrimaryDictSize].code);

code2 = Dictionary[code2 - PrimaryDictSize].nextCode;

}

GIFDrawPixel(code1);

Dictionary[currentDictSize - PrimaryDictSize].code = code1;

Dictionary[currentDictSize - PrimaryDictSize].prevCode = oldcode;

++currentDictSize;

//std::cout << "dictionary size: " << std::dec << currentDictSize << std::endl;

if (currentDictSize == MAX_DICT_SIZE) return -2;

if ((currentDictSize) == (0x0001 << currentCodeSize))

++currentCodeSize;

if (currentCodeSize > 12)

currentCodeSize = 12;

oldcode = code;

}

return 0;

}

int GIF::checkSignature(char * IN){

char signature[7];

int i;

for (i = 0; i <= 6; i++)

signature[i] = IN[i];

if ((strcmp(signature, "GIF87a") == 0) || (strcmp(signature, "GIF89a") == 0))

return 1;

else

return 0;

}

unsigned short GIF::getNextCode(void){

unsigned int retval = 0, temp;

if (bitsRemaining >= currentCodeSize){

retval = (read_code & ((0x01 << currentCodeSize) - 1));

read_code >>= currentCodeSize;

bitsRemaining -= currentCodeSize;

}

else {

retval = (read_code & ((0x01 << bitsRemaining) - 1));

read_file(g_fileObject, &read_code, 1);

++counter;

if (counter == currentDataSectionLength){

counter = 0;

read_file(g_fileObject, &currentDataSectionLength, 1);

}

if ((currentCodeSize - bitsRemaining) <= 8){

temp = (read_code & ((0x01 << (currentCodeSize - bitsRemaining)) - 1));

retval += (temp << bitsRemaining);

read_code >>= (currentCodeSize - bitsRemaining);

bitsRemaining = 8 - (currentCodeSize - bitsRemaining);

}

else {

retval += (read_code << bitsRemaining);

read_file(g_fileObject, &read_code, 1);

++counter;

if (counter == currentDataSectionLength){

counter = 0;

read_file(g_fileObject, &currentDataSectionLength, 1);

}

retval += ((read_code & ((0x01 << (currentCodeSize - bitsRemaining - 8)) - 1)) << (bitsRemaining + 8));

read_code >>= (currentCodeSize - bitsRemaining - 8);

bitsRemaining = 8 - (currentCodeSize - bitsRemaining - 8);

}

return retval;

}

void GIF::GIFDrawPixel(unsigned char code){

COLOR rgbColor;

bool trans_pixel = false;

rgbColor = g_GlobalColorTable[code];

if(trans_gif && code == trans_color_index) trans_pixel = true;

(*gif_draw_pixel)(rgbColor.R, rgbColor.G, rgbColor.B, trans_gif , trans_pixel);

}

基本的に使い方はこのライブラリが紹介してあったサイトのサンプルコードで動きますが、コールバック関数が

(*gif_draw_pixel)(rgbColor.R, rgbColor.G, rgbColor.B, trans_gif , trans_pixel);

で返ってきますので修正してください。デコードしたピクセル毎に呼び出されます。trans_gifは透過GIFファイルかどうか、tens_pixelは透過ピクセルかどうかという変数を加えていますので透過処理も可能となります。これで正しくデコードはできるようになりました。

余談ですが、汎用性・互換性の為、このライブラリもイニシャライズ時にファイルストリームを渡して初期化していますが、強震モニタを作る上で画像生成の流れ的に

GIFダウンロード
GIFデコード
画像処理&合成
TFT出力

のステップを想定しています。結構なメモリが必要ですので、PSRAMがあるESP32-wroverシリーズが必須といえます。この場合は、GIFをダウンロードしたメモリ領域ごとデコーダに渡せるようにした方が便利なので実際はそちらの方で実装しています。

int GIF_MEM::init_decoder(uint8_t * gif, GIF_IMAGE * gifImage) { -略- }

- 略 -

/*
int GIF_MEM::read_file(File fileObject, unsigned char *buf, int count){
  return fileObject.read(buf,count);
}
*/
int GIF_MEM::read_file(uint8_t * gif, unsigned char *buf, int count){
  
	for(int i=0;i < count ; i++){
		buf[i] = gif[gif_file_pos];
		gif_file_pos++;
	}
	return 1;
}

int GIF_MEM::init_decoder(uint8_t * gif, GIF_IMAGE * gifImage) { -略- }

- 略 -

int GIF_MEM::read_file(File fileObject, unsigned char *buf, int count){

return fileObject.read(buf,count);

}

int GIF_MEM::read_file(uint8_t * gif, unsigned char *buf, int count){

for(int i=0;i < count ; i++){

buf[i] = gif[gif_file_pos];

gif_file_pos++;

}

return 1;

}

重複するので全掲載は避けますが、上のような感じで変更します。gifはGIFをダウンロードしたPSRAM上のバッファを想定してます。こうすればSPIFFSやSDカード不要でPSRAM上で処理を完遂できます。

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