### iNES Header Structure and Validation

Source: https://context7.com/cjoudrey/go-nes-tools/llms.txt

Defines the iNES header structure in Go, including magic bytes, PRG/CHR ROM sizes, and flags. Includes an example of validating the iNES magic bytes.

```go
// iNES Header Format (16 bytes)
type iNESHeader struct {
    Constant  [4]byte  // "NES\x1A" (0x4E, 0x45, 0x53, 0x1A)
    AmountPRG uint8    // PRG ROM size in 16KB units
    AmountCHR uint8    // CHR ROM size in 8KB units
    Flags6    byte     // Mapper, mirroring, battery, trainer flags
    _         [9]byte  // Remaining header bytes (Flags7-10, padding)
}

// Flags6 bit 2 indicates presence of 512-byte trainer data
// CHR ROM offset = 16 (header) + 512 (if trainer) + (AmountPRG * 16384)

// Example: Validate iNES magic bytes
if header.Constant != [4]byte{0x4E, 0x45, 0x53, 0x1A} {
    fmt.Println("Not a valid iNES file.")
    os.Exit(1)
}
```

--------------------------------

### Compile chr2png Tool

Source: https://github.com/cjoudrey/go-nes-tools/blob/master/chr2png/README.md

Compile the Go source file to create the executable binary for the chr2png tool.

```bash
go build -o nes-chr2png chr2png.go
```

--------------------------------

### Build and Use chr2png Tool

Source: https://context7.com/cjoudrey/go-nes-tools/llms.txt

Build the chr2png tool and use it to convert CHR ROM data to a PNG image. It can auto-generate the output filename or accept an explicit one. This is useful for visualizing and editing graphics.

```bash
cd chr2png
go build -o nes-chr2png chr2png.go
```

```bash
./nes-chr2png game.chr
```

```bash
./nes-chr2png game.chr sprites.png
```

```bash
../extractchr/nes-extractchr game.nes > game.chr && ./nes-chr2png game.chr tileset.png
```

--------------------------------

### Compile png2chr Tool

Source: https://github.com/cjoudrey/go-nes-tools/blob/master/png2chr/README.md

Use this command to compile the png2chr Go program into an executable binary.

```bash
go build -o nes-png2chr png2chr.go
```

--------------------------------

### Build and Use png2chr Tool

Source: https://context7.com/cjoudrey/go-nes-tools/llms.txt

Build the png2chr tool and use it to convert a PNG image back into CHR ROM format. The input PNG must be paletted, have dimensions divisible by 8, and use a maximum of 4 colors.

```bash
cd png2chr
go build -o nes-png2chr png2chr.go
```

```bash
./nes-png2chr sprites.png
```

```bash
./nes-png2chr sprites.png game.chr
```

```bash
../extractchr/nes-extractchr original.nes > original.chr
../chr2png/nes-chr2png original.chr tileset.png
./nes-png2chr tileset_edited.png modified.chr
```

--------------------------------

### Compile extractchr Utility

Source: https://github.com/cjoudrey/go-nes-tools/blob/master/extractchr/README.md

Compile the extractchr Go program using the go build command. The output executable will be named 'nes-extractchr'.

```bash
go build -o nes-extractchr extractchr2.go
```

--------------------------------

### Build and Use extractchr Tool

Source: https://context7.com/cjoudrey/go-nes-tools/llms.txt

Build the extractchr tool and use it to extract CHR ROM data from an iNES file. It can output to a file or pipe directly to other tools.

```bash
cd extractchr
go build -o nes-extractchr extractchr.go
```

```bash
./nes-extractchr game.nes > game.chr
```

```bash
./nes-extractchr game.nes | ../chr2png/nes-chr2png /dev/stdin sprites.png
```

```bash
./nes-extractchr game.nes > game.chr && ls -la game.chr
```

--------------------------------

### Convert CHR ROM to PNG

Source: https://github.com/cjoudrey/go-nes-tools/blob/master/chr2png/README.md

Use the compiled chr2png tool to convert a CHR ROM file into a PNG image.

```bash
nes-chr2png pong.chr pong.png
```

--------------------------------

### Convert PNG to CHR ROM

Source: https://github.com/cjoudrey/go-nes-tools/blob/master/png2chr/README.md

Execute the compiled png2chr tool to convert a PNG image file to a CHR ROM data file.

```bash
nes-png2chr pong.png pong.chr
```

--------------------------------

### Extract CHR ROM Data

Source: https://github.com/cjoudrey/go-nes-tools/blob/master/extractchr/README.md

Use the compiled 'nes-extractchr' tool to extract CHR ROM data from an iNES ROM file. Redirect the output to a .chr file.

```bash
nes-extractchr pong.nes > pong.chr
```

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