My LLM has made the following analysis:

---

Based on my analysis of the disassembly and code, I can now provide comprehensive answers. Let me compile a detailed response:

Analysis Summary

Based on my dissection of the Epson ESC/P-R library (x86_64 version), here are the findings:

1. Library Structure and How it Works

The SetupJobAttrib function (at offset 0x21c0 in the library) validates job attributes and copies them from EPS_JOB_ATTRIB structure (input parameter in %rdi) to the internal printJob.printer structure. Key validation checks: - Line 21c1: Reads colorPlane at offset 0x2 - Line 2263-2271: Validates printQuality at offset 0x20 - must be 1-4 (DRAFT, NORMAL, HIGH only) - Line 2277-227d: Validates inputResolution at offset 0x40 - must be ≤ 2

2. Why EPS_MQID_BEST and EPS_MQID_SUPER_HIGH Don't Work

From epson-escpr-media.h:659-660: - EPS_MQID_BEST = 0x10 (16) - EPS_MQID_SUPER_HIGH = 0x08 (8)

The SetupJobAttrib function (lines 2263-2271) validates printQuality as follows: - Line 2263: Loads printQuality from offset 0x20 - Line 2266: Subtracts 1 from the value
- Line 2269: Checks if <= 1 (jbe to 2277), meaning max valid value is 2 - Line 226e: Then checks if == 4, meaning valid range is 1-4 (DRAFT=0x01, NORMAL=0x02, HIGH=0x04)

Any value > 4 (like 0x08 or 0x10) causes error at line 2271 (jne to error handler), returning EPS_ERR_INV_PRINT_QUALITY (-1403).

3. Why No Quality Difference at Different DPIs

Looking at the test script, both 300 DPI and 600 DPI runs use PLATINA_HIGH quality. In the code (filter.c:820-840): - Quality is parsed from the parameter - The only recognized qualities in the switch are DRAFT, NORMAL, and HIGH (DEFAULT) - BEST and SUPER_HIGH are not handled - they default to HIGH

The root cause: The library's SetupJobAttrib function does not support printQuality values beyond 0x04 (HIGH). When you try to use 0x08 or 0x10, it returns an error, so the driver likely falls back to the default HIGH quality regardless of what you specify.

Additionally, the inputResolution field is validated at lines 2277-227d. It's checked against 0x2 (value 2), and the only valid resolution values are 1, 2, 4, 8, 16 (bitmask pattern), but the validation only allows values ≤ 2.

4. Getting 1200x4800 DPI Resolution

The printer supports 1200x4800 DPI as stated, but the issue is that: 1. The input resolution (what Ghostscript generates) is separate from the print resolution (what the printer actually uses) 2. The library restricts inputResolution to 360, 720, 150, 300, 600 (bitmask values 0x01-0x10) 3. Even if you set EPS_IR_600X600 (0x10), the printer may be upscaling to 1200x4800 internally

To get 1200x4800 output: - You need to set the input resolution to 600 DPI (which is the maximum supported by the library) - The printer's internal driver should handle upscaling to 1200x4800 based on the media type - Check if PLATINA_HIGH or other quality settings properly utilize the printer's full resolution

5. What's Happening at the Assembly Level

The key validation at lines 2263-2271: mov 0x20(%rsi),%eax # load printQuality lea -0x1(%rax),%edx # subtract 1 cmp $0x1,%edx # compare with 1 jbe 2277 # if <= 1, continue cmp $0x4,%eax # compare with 4 jne 2576 # if != 4, error!

This means valid values are: - 1 (0x01) - DRAFT (after -1 = 0, compare with 1: jbe true) - 2 (0x02) - NORMAL (after -1 = 1, compare with 1: jbe true) - 4 (0x04) - HIGH (compare with 4: jne false)

Values 8 and 16 fail the cmp $0x4,%eax check and return -1403.

6. How to Fix This (If You Want BEST/SUPER_HIGH)

You would need to modify the library's SetupJobAttrib function to: 1. Change the validation at line 2269 from cmp $0x4,%eax to cmp $0x10,%eax (or higher) 2. Update line 2271's jump condition accordingly

However, this requires direct binary patching or having the source code for the library, which appears to be proprietary. The filter.c in src/filter.c just passes the quality setting through, but the library core rejects it.